S H 

337 



DEPARTMENT OF COMMERCE 

BUREAU OF FISHERIES 

HUGH M. SMITH, Commissioner 



SOME CONSIDERATIONS CONCERNING THE 
SALTING OF FISH 



By DONALD K. TRESSLER 

Temporary Assistant, Division of Fishery Industries 



APPENDIX V TO THE REPORT OF THE U. S. COMMISSIONER 
OF FISHERIES FOR 1919 




Bureau of Fisheries Document No. 884 



PRICK, 10 CENTS 

Sold only by the Superintendent of Documents, Government Printine OfSce 

Washington, D. C. 



^g_^ WASHINGTON 

;^ — ^ GOVERNMENT PRINTING OFFICE 



'■oms^ 



¥ 



1920 




Book 



DEPARTMENT OF COMMERCE 
BUREAU OF FISHERIES 

HUGH M. SMITH, Commissioner 



SOME CONSIDERATIONS CONCERNING THE 
SALTING OF FISH 

By DONALD K. TRESSLER 

Temporary Assistant, Division of Fishery Itidustries 



APPENDIX V TO THE REPORT OF THE U. S. COMMISSIONER 
OF FISHERIES FOR 1919 




Bureau of Fisheries Document No. 884 



PRICE, 10 CENTS 

Sold only by the Superintendent of Documents, Government Printing Office 
Washington, D. C. 

WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1920 



/^^ 

d' 



D* Of -^« 

APH 12 



CONTENTS. 



Page. 

Introduction 5 

The need for experimental worli 5 

Present commercial methods of salting fish 7 

Gloucester, Mass 7 

Reedville, Va 9 

Edenton, N. C 10 

Havre de Grace, Md 10 

Boothbay Harbor, Me 11 

Summary 11 

Storage of salted fish 12 

Purpose of experimental work ^ 12 

Factors influencing the salting of fish 12 

Mode of procedure in experimental work 14 

Experimental 16 

I. Influence of impurities in salt in salting fish 16 

Introduction 16 

Commercial sources of salt 16 

Methods of manufacture 17 

Analyses of commercial salts 18 

Infliuence of impurities on rate of penetration of salt 21 

Introduction 21 

Former work on rate of penetration 21 

Importance of rate of penetration 21 

Method 22 

Discussion 23 

Summary 27 

Influence of impurities on rate of protein decomposition 27 

Introduction 27 

Methods 29 

Determination of amino-acid nitrogen 29 

Salting of fish 30 

Analysis of fish 31 

Discussion 32 

Effect of calcium and magnesium salts 32 

Effect of sodium sulphate 33 

Discussion 34 

Physical effects on fish 34 

A possible explanation of results 34 

Practical application 34 

Effect of fineness of salt 35 

Summary 35 

II. A comparison of efliciency of brine and dry salt for salting fish 35 

Introduction 35 

Determination of rates of protein decomposition 36 

Method .36 

Discussion Sd 

Rate of penetration of salt 40 

Method 40 

Discussion 40 

3 



4 CONTENTS. 

Elxperimental — Continued. 

II. A comparison of efficiency of brine, etc. — Continued. Page. 

Discussion 41 

Physical differences between the products of the two 

methods 41 

Hypothesis to account for results 42 

Dry-salt method more economical 42 

Summary 43 

III. Influence of method of cleaning fish for salting 43 

Introduction 43 

Importance of method of cleaning 43 

Commercial methods of cleaning 44 

Effect of cleaning on protein decomposition 44 

Method 44 

Discussion 45 

Action of the skin 47 

Method 47 

Discussion . 48 

Practical applications 48 

Summary 49 

IV. Influence of freshness in salting fish 4^ 

Introduction 49 

Method .tO 

Discussiuu 51 

(ieneral conclusions 53 

llelative importance of factors 53 

Practical applications of results 54 

Bibliography 55 



SOME CONSIDERATIONS CONCERNING THE SALTING 

OF FISH.« 



By Donald K. Tressler, Temporary Assisant, Division of Fishery Industries. 



Contribution from the Fisliery I'roducts Laboratory, Washington, D. C. 



INTRODUCTION. 

THE NEED FOR EXPERIMENTAL WORK. 

Althoiigli fish have been preserved with salt since prehistoric times, 
little experimental work has been done with the view of improving 
the existing methods. The fisherman who salts his own catches of 
fish or who cooperates with his neighbors in salting fish has neither 
the time nor the money to experiment that he may improve his prod- 
uct or save labor and waste products. With a few exceptions, the 
fishing industry has not attracted large capital for extensive opera- 
tions. It has not been exploited, therefore, as has the meat-pack- 
ing industry. 

Much work has been done in the hatching of fish eggs, stocking 
streams and lakes, and increasing the aquatic life of this country 
generally. But until recently little had been done to conserve the 
fish after being taken or to utilize as food fish w^hich had hitherto 
been neglected. Little of the river herring, sea trout, Spanish 
mackerel, kingfish, sea bass, scup, and drumfish in our southern 
waters had been utilized until within recent years, w'hen refrigerator 
cars and cold-storage plants came into use. 

It required the stimulus of the enormous demand for food caused 
by the great w^orld war to awaken an interest in fish salting and to 
arouse a demand for better methods. It became apparent that if the 
methods of salting fish could be improved so that fish might be 
salted with safety during hot weather in any warm climate the food- 
fish supply of the United States would be gi'eatly augmented. 

« This work was undertaken in cooperation with the National Research Council, Council 
of National Defense, and was at first conducted in the laboratories of Johns Hopkins 
University, where the author had the benefit of the advice and direction of Prof. B. B 
Livingston, department of plant physiology, and Prof. E. V. McCoIlum. School of Hygiene 
and Public Health. He is also indebted to Prof. J. J. Abel, of the department of 
pharmacology of the same university, for the use of his laboratory for the conduct of 
part of this work. 

The results achieved, the conclusions reached, and the recommendations made in this 
paper have their origin In experiments done on a small scale and are not to be taken 
as having been proved by commercial practice. 

5 



6 THE SALTING OF FISH. 

There is a lamentable lack of control over the salt-fisR product 
produced in any plant. In some places the standard of quality is a 
white, colorless fish. Yet in those localities it is doubtful whether 
the fish salters understand the factors controlling whiteness. In 
other localities a very hard, rigid fish is desired. In such regions 
there is a great demand for Turks Island salt, for it is quite gen- 
erally understood that this salt produces a hard fish, although very 
few understand why. Before this experimental work had been fol- 
lowed two weeks the experimenter learned that the qualities of the 
finished product, such as color and hardness, could be controlled en- 
tirely. This alone made the work worth while. 

It has long been known that it is exceedingly difficult to salt fish 
in the ordinary way during hot weather, and few attempt it. Ap- 
parently no one had tried to find out why fish spoD so quickly while 
being salted during the summer. 

For centuries fish have been cured either in brine or in dry salt 
without the addition of brine. There has been much discussion con- 
cerning the value of the two methods. It was, therefore, worth while 
to determine the relative merits of the two methods of applying salt 
to fish, even though no information relevant to the problem under 
consideration should be obtained. 

The inexactness of the present methods has been pointed out to 
show the need for such experimental work as is reported in this 
paper. Correct interpretations of experimental work should lead to 
more exact procedure in salting fish. A more uniform product should 
be obtained. The results of the experimental work should explain 
the reason for some of the methods in use to-day. The consideration 
of the scientific aspect of fish salting should bring forth a spirit of 
research for better salt fish. There should be a demand for high 
standards for salted fish. At present in some parts of the country 
the salt-fish buyers have practically no standards for estimating the 
quality of the salt-fish product. This is in part because of the diffi- 
culty in estimating differences in quality of salt fish. 

At the present time (summer or 1919) the price of salt river her- 
ring is very low. This is chiefly because the quality of salted herring 
sold during the past few years has been so poor. The salt river her- 
ring on the market has a very strong " wild-game " taste. If certain 
precautions were taken, this could be entirely avoided. The resultant 
product would then be of much better quality than that to which the 
public is accustomed. It is doubtful if a better price could be ob- 
tained for salt river herring under present conditions. If higher 
standards were demanded, however, it should sell for a higher price. 

In North Carolina and Virginia the buying public has become so 
accustomed to purchasing very hard, dry fish that soft fish in brine 
will not sell, although it may be better in quality. There is little 
ground for the argument that dry, hard fish is of greater culinary 
value. On the other hand, without investigation it would seem rea- 
sonable that a wet, soft fish would be more palatable when cooked 
than a fish " as hard as a board." 

Most fish salters are aware of the fact that they must not store their 
fish in hot places during the summer months: yet no attempt has 
been made to determine the best conditions for storing salted fish. 
Fish have been stored both dry (" tight packed," packed in layers 



THE SALTING OF FISH. 71 

with solar salt between layers of fish) and in brine (pickle) ; yet no' 
investigation has been carried out to show which of these two metli- ! 
ods is the better. The " tight-pack " method is almost universally 
used in the South, whereas in the North fish, with the exception of 
cod, haddock, cusk, and pollock, are just as universally stored in 
brine. 

Much may be done to improve both the methods of salting and of 
storing fish. If better methods were used, salted fish, even the " com- 
mon herring," would regain its place in public favor. The fish Salter 
would gain immensely thereby, for as the quality improves so will 
the demand. It is hoped that this work may be the beginning of a 
movement looking toward a better salted-fish product; that it may 
encourage the fish Salter to control his product and produce a fish of 
the best possible quality. A proper understanding of the factors 
affecting the product will surely lead toward the improvement of 
methods. 

PRESENT COMMERCIAL METHODS OF SALTING FISH. 

The methods of salting fish in use to-day vary greatly in different 
localities. The writer found, in going from one fish-salting plant to 
another, that mam^ fish salters were not familiar with all of the 
methods of salting fish. It is wise, therefore, to give a brief descrip- 
tion of the methods in use in various parts of the country. This will 
make clear the reasons for the procedure followed in the experimental 
work. There may also be a better understanding of these different 
methods, and if they are correctly understood the fundamental prin- 
ciples of salting fish will be clear to the reader. 

In this work no mention is made of the mechanical details of clean- 
ing, hauling, lifting, or drying fish. Attention is given to only the 
important points which affect the quality of the finished product. 
The writer has visited five fish-salting centers and has observed the 
methods employed. The procedure followed in salting fish in these 
places will be described briefly. No attempt has been made to in- 
clude all of the different processes or the procedure for all varieties 
of fish. The description merely includes the most important methods 
and the general procedure. 

GLOUCESTER, MASS. 

In Gloucester the business of salting fish is very extensive. It is 
characterized by greater organization and larger companies than 
elsewhere. The reason for the organization is to be found in the 
large number of fish caught in that vicinity and in the continuity of 
the catches. Fish are brought into Gloucester in large quantities 
every working-day of the year. Employees may, therefore, be hired 
for the entire year and the plants worked on a larger scale than else- 
where. 

The cod, haddock, cusk, and pollock are caught together and are 
salted in the same general way. When they are unloaded from the 
vessels, the fish are sorted as to kind and size. During the cold 
months these fish are salted either in kenches (regular piles or layers 
of fish) or butts (very large barrels, of about 300 gallons capacity). 
In the warmer months all are salted in butts, as the fish would spoil 



8 THE SALTING OF FISH; 

if they were not covered with pickle durinoj the " striking " or salting 
process. The fish are thrown " face up " (cut surface, flesh side up) 
into the butts and sprinkled with salt as thev are thrown in. Great 
stress is placed upon the even distribution of the salt. Between 6 
and 7 bushels are used to each butt of fish. Turks Island salt is 
ordinarily used. Each butt yields approximately 500 pounds of dried 
cod. The rule holds : The warmer the weather the more salt used. 

The fish are piled high above the top of the butt. The last few 
layers, those exposed, are piled with the backs up. A pile of salt is 
placed upon the top of the fish. By the day following the salting, 
the fish have settled below the top of the butt and the pile of salt 
has almost disappeared. Five or six more pecks of salt are then 
added to strengthen the piclde. Ordinarily the fish are allowed to 
remain in the butts from 10 days to 3 weeks. Only 3 days are re- 
quired for the salt to penetrate through the fish, the remainder of the 
time being required for the fish to " strike through," or harden. 
After 3 days the flesh of the fish is still quite soft, but during the 
next 18 days it gradually becomes harder. If there is a large supply 
of fish on hand and if the demand is slack the fish are left in the butt 
much longer than 3 weeks. However, if allowed to remain there 
for too long a time the salted fish become yellow. This happens in 
the space of 2 months or less in hot weather, but in cold weather 
the fish may be left in the butts almost indefinitely. The amount of 
salt added (6 or 7 bushels) is far in excess of the amount actiuilly 
taken up by the fish and dissolved in the pickle. This excess salt is 
used later in making more pickle. 

After the fish are " struck " they are taken out of the butts, the 
slime is washed off, and the fish are piled in kenches about 4 feet 
high, face up, with the exception of the last few layers, which are 
piled face down in order to keep the top layers clean (free from 
dust). Weights are placed on top of the kenches to compress the 
fish and to squeeze out the pickle. Since the object of the kenching 
is to allow the fish to drain and partially dry, they are piled on racks 
about 8 inches above the floor. This enables the pickle to run out 
from under the piles of fish. The length of time during which the fish 
are left in the kenches depends mainly upon the weather and upon the 
amount of fish already upon the flakes. (See below.) During warm 
wa^ather the fish are likely to spoil, so they are watched very closely 
and are repiled whenever there is danger of spoilage. The more 
often the fish are repiled the less time they must remain on the flakes ; 
but the fish salters usually do not repile them more than once, since 
it requires a great deal of time. However, if the season is a rainy one, 
and they do not dry rapidly upon the flakes, the fish are rekenched 
several times. 

After the fish are somewhat dry they are placed upon flakes for 
further drying. A flake is a rack" (a lattice bed about 8 feet wide) 
built in the open, about 30 inches above a floor. The drying yard is 
known as the flake yard and is often located on a roof. The degree 
to which the fish are dried depends upon the trade. If the fish are 
to be sold in the southern States, they must be drier than if they 
are to be sold in the iininediate vicinity. The length of time the fish 
must remain upon the flakes to dry to the re(iuired degree depends 
entirely upon the weather. The lower the humidity, the less time is 



THE SALTING OF FISH. V 

required for drying. The higher the velocity of the wind, the more 
rapidl}' the fish dry. When there is a driAdng wind two or three 
lots may be dried in a single day. When the weather is poor, how- 
ever, it may take a week or more to dry a single lot. If the sun is 
hot, great care is taken to prevent the fish from becoming sunburned. 
Canvas is placed a few feet above the flake, and this prevents the 
direct-burning action of the sun. When the day is too hot, the fish 
are not placed upon the flake. If rain is imminent, tliey are collected 
and put under Avaterproof boxes on the flakes. 

After drying, the fish are sorted as to quality and size. A first- 
quality fish should be uniformly white, have no bloodstains, possess 
a " sweet " smell, and be one of the thicker fish. After the fish are 
sorted they are hauled to the packing room. Before packing they 
are sprinkled with salt containing 0.4 per cent boracic acid, the 
amount of this mixture applied depending upon the climate of the 
region where the fish will be sold; the warmer the climate, the more 
of it used. This sprinkling of the dried fish with boracic-acid mix- 
ture is peculiar to this class of fish. No other salt fish is piled in 
kenches or dried on flakes. If the fish is for export, it is tied in 
bundles and packed in boxes or drums. 

Although the method of cleaning, the cut appearance of the 
various fishes, and the amount of salt used all differ, mackerel, whit- 
ing, alewives, and herring are usually salted by the same general 
method in Gloucester. The exact procedure followed in salting one 
particular fish varies with the season and the trade, however. 

The cleaned (cut) or round (uncut) fish are dipped in salt, the 
fineness of the salt and the quantity used depending upon the variety 
of the fish and the season of the year. The dipped fish are packed 
in layers in barrels or butts, salt is scattered over each layer, and, 
as in the case of cod, a small pile of salt is placed on top of the fish. 
The fish are then allowed to make their own pickle, and within 24 
hours enough has been formed to cover them. The pile of salt on 
top of the fish is replenished on the second day. 

Ample time is alloAved for the fish to become thoroughly " struck,'' 
or salted, before they are touched again. This period is usually at 
least 30 days. The fish are then repacked tightly in barrels. In most 
cases a small amount of salt is placed over the top. The barrel is 
then headed and a bunghole bored in it, after which it is rolled on 
its side and filled with 100° brine (saturated salt solution). 

REEDVILLE, VA. 

Along the Chesapeake Bay, in the vicinity of Reedville, Ya., there 
are about 40 fish-salting plants. Almost the only fish salted on a 
large scale is the alewife, or river herring. There is little organiza- 
tion among the fish salters of this region, due, in part, to the very 
short season. At Irvington the plants often operate no longer than 
six days. At Reedville the plants operate for about three weeks; 
however, the rush season lasts onlj? a week. 

The packers in this vicinity salt fish in a way distinctly different 
from that used in any other section of the country, Avith the excep- 
tion of Havre de Grace, where for the most part, a similar method is 
used. The washed, cut river herringi are dumped into large vats filled 

148957°— 20 2 



10 THE SALTING OF FISH. 

one-sixth full with 100"^ pickle (saturated suit sohition). Xs the fish 
are placed in the tanks salt is scattered over each layer. Each day 
the fish are roused (stirred up) with large paddles and more sait is 
added, usually in sufficient quantity to make the pickle saturated 
(100°) ; but the procedure varies in the different plants. Some fish 
salters (those in the vicinity of Irvington) keep their brine at 70 
per cent saturation (70°). Even if the brine used at the start is 
saturated, by the following morning, when the fish are stirred for 
the first time, the pickle is not stronger than 60°. If a very large 
excess of salt is added when the fish are put in, this lowering of the 
concentration of the salt solution may be obviated to a considerable 
extent; but, as the fish ai-e immersed loosely in a large excess of 
pickle, there is a tendenjcy for the salt to sink to the bottom of the 
vat. As a result the pickle on top is always below saturation, 
whereas the bottom layers are saturated, or very nearly so. 

At the end of from 7 to 10 days the fish are scooped out of the 
vats and hauled to a draining floor, wliere they are placed loosely in 
piles about 18 inches deep. They are allowed to drain and dry for 
three or four days. Then the salted river herring are packed tightly 
in layers in barrels, and a quart of Turks Island salt is scattered 
between each two layers of fish. No brine is added to these barrels, 
as the fish are sold dry. It is to be noted that in this region brine is 
added to the fish when they are salted, and aftei- salting they are 
sold dry; whereas in Gloucester the alewives are salted with dry 
salt, without the addition of brine, and are sold in brine (pickle). 

EDENTON, K. C. 

Most of the fish salted in this region are river herring, or alewives. 
Most of the fishermen salt their own catches of fish. The fish -salting 
plants are, therefore, small, even smaller than those in the vicinity 
of Reedville. The season here is also short, usuallj' lasting about 
six weeks. 

In this region greater care is taken to wash the cut (cleaned) fish 
more perfectly. As a result, the salt river herring produced is of a 
little better quality than that produced elsewhere. The fish are mixed 
with salt with shovels and are shoveled into butts without any par- 
ticular packing. The}' are allowed to remain in the butts from 8 to 
12 days, after which they are piled on the floor to dry and drain for 
three or four days, in the same way that they are handled at Reed- 
ville. They are then packed tightly in barrels. About a quart of 
Turks Island salt is scattered over each layer of fish; no brine is 
added. 

HAVRE I)E ORACE, Afn. 

In Havre de Grace practically the identical procedure is followed 
in salting fish as in Reedville, Va. Aside from one plant, in which 
some fish are salted by a modified "Scotch" method, there are no 
iniportant differences from the Reedville method. This modified 
"Scotch" method involves the salting of the round (uncut) alewives 
with dry salt. The fish are packed tightly in barrels, covered, and 
allowed to develop their oAvn pickle. This method is similar to the 
one followed at Boothbay Harbor. However, at Boothbay Harbor 



THE SALTING OF FISH. 11 

the fish are " gibbed " or " pipped." That is to say, the gills are 
cut out, and the viscera, with the exception of the roe or milt, are 
pulled out. The fish are sold in brine. 

BOOTIIBAY HARBOR, ME. 

Herring is the principal fish packed in Boothbay Harbor. JSIost 
of the fish are Scotch-cured here. In this process the pipped fish are 
mixed with fine salt by hand without being washed. They are then 
carefully packed in barrels. Salt is sprinkled over each layer. A 
day or so later the barrels are filled up with herring of the same day's 
pack. After 9 or 10 days the barrel is drained of the old pickle, and 
the fish are washed with it without unpacking. The barrel is then 
completely filled with fish and filled through the bunghole with 
100°, or full-strength, brine. The peculiarity of this method is that 
the fish are not washed before being salted. Therefore, every bit of 
blood in the cut fish either remains in the fish or goes into the pickle. 

SUMMARY. 

As stated previously, no effort has been made to include all the 
variations of the different methods of salting fish. Neither has 
any attempt been made to discuss anj'' detail other than the mode 
of applying the salt to the fish. From the above description it is 
seen that all the methods include but three general modes of appli- 
cation of salt to fish: 1. The fish are immersed in a solution of salt 
which is kept saturated, or nearly so, by the addition of salt from 
day to day. 2. The fish are packed in water-tight containers with 
dry salt and are allowed to develop their own pickle. 3. The fish 
are packed in piles (kenches). and the pickle is permitted to run off 
the fish as it is formed. 

The last-mentioned method is used only in cold weather, in an 
emergency when there are no containers at hand. Such is often the 
case on ships fortunate enough to make extraordinarily large catches. 
As it is practical only in cold weather, the method is not available 
for much commercial fish salting, and therefore no experimental 
work with it has been attempted. 

The brine method of salting fish is chiefly used along the Chesar 
peake Bay, in the Reedville (Va.), and Havre de Grace (Md.) re- 
gions. This method has the big disadvantage of requiring more labor 
than the dry-salt method. Some salt must be added nearly every 
day, and the pickle must be watched closely to prevent it from be- 
coming too weak. The fish must be roused (stirred up) every day. 
This is done with large paddles of various sizes and shapes and re- 
quires the expenditure of considerable energ}'. The fish produced 
by this method are much softer and contain more water than those 
produced by the dry-salt method. They appear similar to partially 
" struck," dry-salted fish. However, the fish are more plump and 
seem more like fresh fish than the dry-salted product. 

The dry-salt method inA^olves no rousing after salting and necessi- 
tates but one addition of salt, provided the fish are properly salted in 
the beginning. Usually the fish salted by this method are tightly 
packed in barrels or butts and not disturbed. This prevents the salt 
from falling to the bottom, as is the case when the brine-salted fish 



12 THE SALTING OF FISH. 

are roused. Fewer scales are knocked off, and the fij^ have a 
wrinkled, shrunken appearance. If a lot of dry-salted fish is mixed 
with a lot of brine-salted fish, the fish can easily be separated, so 
marked is the difference in their appearance. 

STORAGE OF SALTED FISH. 

There are three general methods of storage: 1. the brine: 2. dry, 
with salt; 3, dry, with boracic acid. The quality of the fish on the 
retail market depends to a considerable extent upon the temperature 
and method of storage. No experimental work on storage Avas done. 

The fish are kept in their own pickle or put in fresh stiturated 
brine, or packed dry. If the pickle formed by the fish is dirty in 
appearance, it is discarded and fresh pickle (salt solution) is added. 
New brine is always added if the salt fish are likely to be stored in a 
place which is not cool. Fish dealers say that the " blood pickle " 
is likely to " sour " if kept in a warm place. 

If the fish are packed dry, as are the cod in Massachusetts and the 
alewives in the South, they are packed either with salt or with 
boracic acid. The cod is sprinkled with salt containing 0.4 per cent 
boracic acid before packing. A considerable quantity of coarse salt 
is thrown over each layer of alewives as they are packed in the 
barrels. 

In all cases the salted fish must be kept at a low temperature if 
they are to be stored for any length of time. The fish salted in 
Massachusetts and Maine are held in cold storage until the time of 
shipment. In North Carolina and Virginia the fish are held in 
" cool storage." Fish stored exposed to the air are very likely to 
" rust." Kusting is due to the oxidation of the fish oil and gives the 
fish a dark-brown color. Packing in brine prevents this to a large 
extent. 

PURPOSE OF EXPERIMENTAL WORK. 

This work was instituted in order to work out, if possible, a 
method of salting fish applicable in warm climates. At present 
none of the methods known are applicable for commercial purposes 
in a climate where the temperature averages above 70° F. Great 
care must be taken if the mean temperature rises above 60° F. The 
logical way to work out any new method is to study the existing 
methods first. This study should show whether some method in use 
to-day can be so improved that it may be used at a higher tempera- 
ture. If, after the present procedures have been given a trial and 
their shortcomings discovered, no existing method can be adapted for 
warm climates, then the need for a new method will be shown. 

FACTORS INFLUENCING THE SALTING OF FISH. 

At the beginning it was evident that, if the various inethods 
were to be fairly judged, the influence of the factors affecting the 
.salting of fish would have to be known. Then, if all known methods 
were foimd incapable of being modified for use at higher tempera- 
tures, the relative values of the various factors would have been 
found, and improvements in the present methods mi^ht be sug- 
gested without further work. There would also be a basis of knowi- 



THE SALTING OF FISH. 13 

edge with which a new method could be worked out. Besides, this 
phm of procedure would give data of great value. The application 
of correct interpretations of these data would lead to improved 
methods and a more uniform product. The relative importance of 
the factors influencing the salting of any fish being then known, the 
fish Salter should be able to produce any desired product by modify- 
ing his conditions. 

It has always been known that the relative freshness of a fish has 
an influence upon the quality of the salted fish. Everyone is aware 
of the fact that if fish are stale great care must be exercised in salt- 
ing them in order to obtain a desirable product. There are no data 
in the literature which show how stale a fish may be and yet be 
salted satisfactorily. This result depends upon the efficiency of the 
method. 

Any method that may be used to salt fish at high temperatures 
may also be used to salt stale fish. Since there is so little control 
of the present method of salting, little valuable data on this process 
could be obtained unless the available methods of salting fish were 
standardized so that uniform procedure would be followed in all 
cases. 

Commercial fish salters are often very careless in allowing their 
fish to become stale before they salt them. The writer found it 
necessary to obtain the maximum temperature of salting perfectly 
fresh fish. Evidently the thoroughness of cleaning and washing the 
fish has an influence on the temperature at which they can be salted 
and also on the quality of the product. It is a well-known fact 
that unbled animals have a " wild-game " taste. The chief differ- 
ence between the taste of domestic ducks and wild ducks is due to 
the fact that wild ducks are shot and not properly bled, whereas 
domesticated ducks are carefully bled. Fish salters fvre well aware 
of the fact that more care must be taken in the salting of round or 
uncut fish than in curing cut fish. Blood, milt, and roe are sub- 
stances which decompose readily. Is it not possible that the presence 
of these substances in fish lower the maximum temperature at 
which they can be salted? 

In the description of methods it was mentioned that there are three 
ways of applying salt to fish. The kench method of dry salting can 
be used in only cold weather. Prior to these experiments no one had 
shown which of the other two methods was the better during hot 
weather. In Massachusetts the dry-salt method is used the year 
around ; yet in Virginia the fish salters are firm advocates of the brine 
method. 

The resistance of the skin to the penetration of salt is another fac- 
tor of importance in salting fish. Almost every fish Salter will 
inform you that the salt penetrates more rapidly through the cut 
surface of the fish than through the skin. Would it not, then, be 
feasible to skin the fish before salting in warm weather? 

Different modes of procedure are followed when various kinds of 
fish are salted. This in itself is evidence that the species of the 
fish is an important factor to be considered when working out any 
method of salting fish. • The amount of fat in the different species of 
fish varies greatly — ^from about 0.09 per cent in cod to about 16.2 
per cent in fat mackerel. The fat in a fatty fish might alter the 



14 THE SALTING OF FISH. 

permeability of a fish to salt. The fat of different fishes vafies widely 
in chemical composition and physical constants. Some fats may 
spoil more readily than others and thus affect the keeping qualities 
of the fish. Fish of different species vary in chemical composition. 
Everyone knows that some fish soften and spoil much more reatlily 
than others. Fish of the same and different species vary gi^eatly in 
size. The surface exposed to the salt depends upon the size and 
shape. 

MODE OF PROCEDURE IN EXPERIMENTAL WORK. 

The chemical changes which fat undergoes during salting and 
storage were not studied, so that an}- points presented on this sub- 
ject are merely casual observations which the experimenter noted 
during his work. The wiiter used but four species of fish in this 
work; naturally, therefore, it is not certain that the work applies 
to all varieties of fish. Most of the work was done with the sque- 
teague {Cynoscion regcdis) and the alewives {Ponwlohus (vsticidis 
and pseudoharengus) . No marked differences were observed in the 
changes taking place during the salting of these fish. The writer 
ventures the opinion that the rules observed as to the protein decom- 
position (flesh decomposition) will apply to nearly every species 
of fish; but he doubts whether any observations concerning the 
chemical changes occurring in the fat of one species will hold good 
for all others, for the various fat constants of the oil of different 
species vary considerably. The rate of oxidation of these fats would 
vary nearly as much as the composition, because certain fish oils are 
much less saturated than others and would oxidize much more 
readily. 

With the ebxception of the chemical changes taking place in the 
fat and the fact that the species studied were few in number, the 
writer believes that he has covered in this paper all of the most 
important factors influencing the salting of fish. The two factors 
not studied in detail embrace such a large amount of work that 
they were considered as separate problems. 

Few important chemical investigations concerning the salting of 
fish have been carried out. Previously the problem had been con- 
sidered mainly from the bacteriological standpoint. Various investi- 
gaticms concerning bacteriological problems had been attempted, 
but no methods of estimating the rate of salting, the rate of protein 
decomposition, or the freshness of fish were to be found in the litera- 
ture. The investigator had, therefore, to work out and standardize 
methods applicable for his purpose. This in itself was no small 
task. The writer does not claim that the methods used are perfect 
or that other procedures could not be used to better advantage but 
rather admits that they may be improved upon. However, the pro- 
cedure was uniform, and the results obtained checked satisfactorily in 
most cases. They must, therefore, be accepted as relative if not exact. 

It seems obvious that the more rapidly salt penetrates the flesh 
of the fish the sooner decomposition of the tissue will stop. This 
{Statement is based on tlie assumption that decomposition of the 
tissue ceases when the fish is thoroughly salted. But this is not 
exactly the case. Decomposition is not stopped ; it proceeds almost 



THE SALTING OF FISH. 15 

infinitely more slowly. The decomposition products are also 
cliang-ed in nature, but no toxic compounds are developed. Later 
the salted fish may spoil because of unfavorable storage conditions, 
Jbut it is not likely that the spoiled fish will produce harmful results 
if eaten. In order, therefore, to learn how fast salt penetrates a fish,, 
a method was required Avhich would enable the experimenter to 
determine the rate of penetration. This should enable him to judge, 
at least from one standpoint, the value of different salts. 

The rate of penetration of salt into fish was followed by cutting 
sections of the fish at different depths from the surface. Tliese sec- 
tions were ashed and the amount of chlorine in them determined. 
The amount of chlorine in the dry salt fish was then calculated. 
This was done from day to day, and thus the increase in salt con- 
tent of the inner sections was determined. The rate of penetra- 
tion of any salt into fish is not an absolutely accurate criterion for 
judging the quality of that salt, for certain impurities in the salt 
migTit have a preservative action surpassing that of the salt. 

Then it was necessary for the experimenter to learn the best method 
of cleaning fish preparatory for salting and to judge the necessity of 
absolute freshness. The rate of penetration does not afford a means 
of judging between two methods of application of the salt. It 
was necessary, therefore, to choose some means of estimating the de- 
composition of the flesh of fish and to adapt it for use with salt 
fish. A wide choice was not permissible, for a very large number of 
determinations must be run simultaneously and quickly. The ap- 
paratus required had to be simple and easily transported, as it was 
necessary to take the laboratory to the fish, as it were, in order to 
obtain fresh fish. The estimation of the rate of amino-acid forma- 
tion was chosen as an indicator of the rate of protein decomposition. 
The reasons for this choice will be explained further on. 

A limited amount of histological work was carried on in order 
to determine if possible the difference between the effect on the cell 
structure of the salted fish of pure sodium chloride and of sodium 
chloride adulterated with other chlorides. A complete record Avas 
kept of the macroscopic changes of each lot of fish. All the ordi- 
nary qualities were observed, such as color, odor, hardness, brittle- 
ness, taste, and general appearance. For the sake of brevity only 
the most notable changes are recorded in this paper. All edible 
.samples of salted fish were cooked at the end of the experiments and 
their palatability noted. In these culinary experiments the fish 
were cooked in such a way that their flavor was in no way disguised. 

The writer presents in this paper only those conclusions that seem 
to him to have been proved beyond doubt. The results may be ac- 
cepted as facts for the river herring and the squeteague. It is very 
probable that they hold for other fish, but further work nnist be done 
to prove this point be^^ond doubt. In no case are the figures abso- 
lutely exact; but there is little doubt that they are relative to each 
other and that they may be compared with confidence. The 
writer hopes that this research will create such an interest in the 
chemistry of fish salting that other researches of a similar nature 
will be instituted. 



EXPERIMENTAL. 

I. INFLUENCE OF IMPURITIES IN SALT IN SALTING FISH. 
INTRODUCTION. 

Nearly every fish Salter is a firm advocate of the use of some brand 
of commercial salt. A few fish salters realize that the foreign solar 
salts produce fish of a quality different from the domestic vacuum 
pan salts, but nearly all of these fishermen think that the difference 
in the product is caused by the variation in the size of tlie salt grains. 
Yery few think that the impurities in the salt affect the liai-dness. 
whiteness, and other properties of the salted fish. Only a few salters 
understand the real meanings of the trade names by which the salt 
is sold. Many believe that " ground alum " refers to the quality of 
the salt sold under that name and would be surprised to learn that 
this name refers merely to the fineness of the salt. 

Fishermen say : " That grade of salt rots fish." Tlie action of the 
salt on fish is not clearly miderstood by all fish salters and salt deal- 
ers. This work on the influence of impurities is worth while, even 
if it merely explains the effects of the common impurities in salt. 
This will give the fish Salter some criterion for judging the value of 
the various salts. 

COMMERCIAL SOURCKS OF SALT. 

The greater proportion of the salt used in this country previous to 
the war was solar salt prepared in Europe or in the West Indies. 
Most of this European salt is made by evaporation of sea wjiter 
along the coast or on islands in the Mediterranean Sea. The chief 
reason for the use of this salt is the cheapness of transportation 
facilities from those parts of the world to the Atlantic seaboard, 
where most of the European salt used in America is consumed. A 
great deal more material is exported from the United States to 
Mediterranean ports than is imported from these ports. Steamers 
are xery anxious to bring cargoes from tbe Mediterranean Sea to the 
Atlantic ports, and therefore they are willing to transport the salt 
to our shores for a very small price. 

However, during the war this supply was almost cut off. The 
price of salt in the United States rose to a very high figure, and 
the greater proportion of the salt used was domestic. Fish salters 
who had previously been prejudiced against the use of American 
salt were forced to use it. and many of them became convinced that 
it was eq\ial in quality, if not superior, to foreign solar salts. 
16 



THE SALTING OF FISH. _ 17 

METHODS OK MANUFACTURE. 

Domestic salt is prepared by one of the following processes : Steam 
evaporation, vacuum evaporation, direct-heat evaporation, or solar 
evaporation. 

Most of the salt produced in the eastern part of America, close to 
the regions where fish are salted, is manufactured by steam evapora- 
tion. The product produced by this method, in jacketed kettles, 
grainers, and vacuum pans, is a fine-grained salt. For some reason 
there is much prejudice against the use of fine-grained salt for fish 
salting. Because of this prejudice very little salt produced in this 
way was used by fishermen previous to the war. During the war, 
when the supply of coarse-grained salt was limited, a large propor- 
tion of the fish salters began the use of fine-gi^ained salt partially to 
replace the coarse-grained salts. 

The salts produced by direct-heat evaporation are usually coarser 
grained than those produced by steam evaporation. To-day this 
process is seldom used except where it is possible to utilize waste 
jlieat, and since such a small amount is prepared in this way, this 
method of production is not considered an important factor in the 
salt supply. 

Unfortunately for the fish trade, nearly all of the domestic solar 
salt is produced in the arid regions of the West. The only place in 
the East where this method of evaporation is practiced is in the 
vicinity of Syracuse, N. Y. Because of the very high freight rates 
eastward across the continent, the cost of the western solar salt on 
the Atlantic coast is almost prohibitive. 

Pure salt is pure sodium chloride. There is no brand of commer- 
cial salt on the market that is 100 per cent pure. There are, however, 
salts on the market which are 99.95 per cent pure. Most of the 
American salts are of greater ]iurity than the foreign salts; however, 
there are a few British salts of great purity. The limited analytical 
data available to the author indicate that British salts, with the ex- 
ception of Turks Island are, on the whole, of much greater purity 
than French, Spanish, and Italian salts. The reason for this prob- 
ably is to be found in the method of manufacture. The southern 
European salts are mainly solar salts, whereas the British salts, be- 
cause of the climate, nuist be prepared in some other way. 

The ordinary procedure in the preparation of solar salts is to allow 
sea water at high tide to run, or be pumped, into low-lying lands, 
forming ponds. The outlet to the sea is then closed, and evaporation 
is allowed to proceed. As the brine becomes more concentrated and 
more nearly saturated it is run into other ponds. Finally, when the 
saturation point has been reached the brine is run into crystallizing 
ponds. Here the usual procedure is to allow evaporation to proceed 
until the brine becomes high in magnesium chloride and low in 
sodium chloride. Usually when a concentration of 32° B. is reached 
the mother liquor is drained off and discarded. From the above 
brief description of the process it will be seen that solar salt is likely 
to be impure. Since sea water is high in calcium and magnesium 
chlorides, it is likely that solar salt will be high in these constituents 
if it is crystallized but once. 

148957°— 20 3 



18 



THE SALTING OF FISH. 



ANALYSES OF COMMERCIAl. SAI-TS. 



The following are analyses of various typical commercial brands 
of salt: 

Analyses or Vakioits Salts Used for CtTsiNG Fish." 



Sodium chloride 

Calcium chlo.ide 

Calcium sulpliate 

Mapiesium clilorido. 
Magnesium sulphate. 
Sand 



I>eterniinalions. 



Italian 

salt. 

Tra- 

pani.'' 



Per cent. 

95.82 

.32 



1.19 
1.75 
.15 



Spanish 

salt, 

Triza.* 



Per cent. 

98.05 

.49 



.80 
.06 



Domestic 

salt, 

IJiamond 

Flake, c 



PfT cent. 
99.78 



.37 
.00 
.00 
.00 



"The sulphates were all calculated as ma,?ne.sium sulphate and the calcium as chloride, except in the 
case of Diamond Flake salt, where no magnesium was foimd. In this case the sulphate was calculated 
as cal?ium sulphate. 

* These results were calculated to a moisture-free basisfrom the data in the table, page 18, Bitting, A. W., 
Bureau of Chemistry Bulletin No. 133. 

c Analyst, J. V. Stepbl. 



THE SALTING OF FISH. 



19 






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20 



THE SALTING OF FISH. 









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THE SAIiTING OF FISH. 21 

These analyses are given in order to sliow the large amounts of 
impurities contained in some salts and to point out that it is possible 
to purchase on the market salts that are very nearly pure. It is to 
be noted that the chief impurities are calcium, magnesium, and sul- 
phates. It is not known in just what chemical combination these 
occur in the salt, but this makes no difference. The analyses are given 
on a nioisture-free basis in order that they shall be relative to each 
other. Further, the amount of moisture contained in salt is of little 
importance to the fish Salter; except that, of course, damp salt con- 
tains less salt per ton than dry salt and, therefore, is more expensive 
if it is purchased at the same price. 

INFLUENCE OF IJMPTJRITIES OX RATE OF PENETRATION OF SALT. 

INTKODTJCTION. 

Former work on rate of penetratiov . — Bitting (1911), of the 
Bureau of Chemistry, tried some experiments to show the effect of 
fineness of salt upon the rate of penetration of salt into codfish. 
Bitting's data show that in various coarse and fine salts there was 
little difference in the rate of extraction of water from the tissues 
or in the rate of penetration of salt into the fish. However, in his 
work no consideration was given the chemical composition of the 
salt. To make the work comparative, a single salt ground to dif- 
ferent degrees of fineness would have to be used in salting all of the 
experimental lots of fish. Bitting used various domestic and for- 
eign salt's which were of different degrees of fineness, but which 
varied widely in chemical composition. It is stated that the cod 
used w'ere small in size, but no information was given regarding 
the uniformity of size, which is a very important factor, as salt 
will penetrate to the center of a thick fish much less readily than 
it will penetrate a thinner fish. Nor does Bitting give any informa- 
tion as to his method of obtaining a 50-gram sample from a fish. 
Before the experiments could be repeated the exact size of the fish 
used would have to be known and also the exact method of sampling. 
The writer doubts that any method of sampling a fish other than 
sampling a section of given thickness a definite distance fi'dm the 
skin or flesh side of the fish would be accurate enough to show dif- 
ferences in the penetrating powers of different salts. 

Importcmce of rate, of penetration. — A consideration of the cause 
of souring had suggested that the souring is a decomposition of the 
inner meat of the fish before the brine strikes through and stops the 
decay. Various writers had observed an antagonism between the 
bivalent metals and monovalent metals in their passage through 
membrane. This suggested that the small amounts of calcium and 
magnesium, which exist in commercial salt as impurities, might exert 
a pronounced retardation on the penetration of the sodium chloride 
into the fish. An attempt was, therefore, made to measure the in- 
fluence of these metals on the penetration of the sodium chloride into 
fish. If it were found that these impurities in salt caused the salt to 
penetrate more slowly, then the use of purer salt would lessen the 
danger of spoilage, for the fish would strike through more rapidly 
and less time would be allowed for decay of the inner portion. 



22 THE SALTING OF FISH. 

An attempt was, therefore, made to measure the rate of penetra- 
tion of pure salt into fish as compared with the rate of penetration 
of mixtures of sodium chloride with the common impurities in salt; 
that is calcium, magnesium, and sulphate. 



It was fortunate that the writer began his experiments on the 
rate of penetration of salt with chemi( ally pure sodium chloride, for 
this led to the discovery that the impurities in salt were largel}- re- 
sponsible for the physical characteristics of the salted fish. The 
fish chosen for this work was the squeteague or weakfish {Cynosc'ton 
regalis) , which could be obtained in a nearly fresh condition almost 
all the year around in Baltimore, where the experimenter was work- 
ing. This fish is of medium fatness and was obtained on the nuuket 
in quantity at any desired uniform size. It had been planned to 
try any improvement that might be worked out on the alewife or 
river herring. The squeteague was more similar to the river herring 
than any other fish that could be purchased throughout a long 
season. 

After considering man}' possible methods of determining the rate 
of penetration of salt into fish it was decided to determine the per 
cent of chlorine in different sections of the fish from day to day. 
The layer from one half to 1 cm. in depth was found by experience 
to give the most uniform results. 

Thus far the work has been applied to but one fish, the squeteague. 
The writer does not claim that the results of the work on this one fish 
can be applied without change to all varieties of fish. Different 
results might be obtained if a fat fish, such as the mackerel, had 
been used. Clark and Almy (1^18) give the fat content of a com- 
posite sample of wealcfish, on May 1, as 2.34 per cent (fresh basis) ; 
on September 25 a similar composite sample contained 0.52 per cent. 
However, they observed also that different s(|ueteague in the same 
school and various schools differ greatly in their fat content. 

Fish in good condition and of as nearly uniform size as possible 
were obtained from wholesale fisli dealers of Baltimore. After cut- 
ting the length of the bell,y, eviscerating, and removing the heads, 
they were salted with dry salt of knoAvn composition. The salt used 
was Baker's analyzed, chemically pure sodium chloride, or mix- 
tures of this M'ith other salts of the same grain size. This salt was 
just a little smaller grained than ground alum, or packer's salt, 
which is so widely used in the fish-salting industr}'. The salts were 
thoroughly mixed, so that all portions were of uniform composi- 
tion. The fish were rolled in salt, and salt was sprinkled over each 
layer of fish, as is the practice of the trade. For every three parts, by 
weight, one part of salt was added when fii-st salted. 

After the fish had been in salt 24 hours one part, by weight, of 
salt was added for every 15 parts of fish. Later, at the end of six 
days, 1 part, by weight, of salt was added for every 30 parts of 
fish. The fish were placed belly down in 2-gallon stone jars. The 
above procedure was carried out in order to duplicate, if possible, 
the method of salting fish in use at Gloucester. 

In the different experiments the temperatuj-e of salting was kept 
as near 68'^ F. as possible by surrounding the jars with running 



THE SALTING OF FISH. 



23 



water near this temperature. The temperature did not vary more 
than 2.7° from the average. The fish were sampled at about 48- 
hour intervals. In sampling, a transverse section, about 3 inches in 
width, was cut from a fish, A layer, 0.5 cm. in depth, was cut from 
the outside of the fish, which had been exposed to the brine. A 
second layer, underlying first layer 0.;") cm. thick, was then cut for 
a second sample. These samples were then dried at 100° C. and 
ground up. The percentage of chlorine was then determined by 
first carefully ashing the fi.sh in silica dishes and afterwards titrating 
the chlorides with tenth-normal silver nitrate, using potassium chro- 
niate as indicator. The inner section (one-half to 1 cm. in depth) 
was found to be of the most uniform composition. Analysis of dif- 
ferent fish from a single lot showed that this layer did not vary 
more than 1 per cent in chlorine. 



DISCUSSION. 



The results of the work which has been completed are given in 
Tables 1 to 4 and are shown graphically in the curves, figures 1 to 4. 
The work shown in Tables 2. 3, and 4 was all done at the same time 
with fish of the same relative fieshness, and the temperatures of the 
brines Avere kept uniform. The work reported in Table 1 was done 
at a different time wdth a different lot of fish of somewhat larger, aize 
and heaviei^ scale. As a result, the data in Table 1 are not comparable 
with those given -in the other tables. 

The results of the analyses of the dry fish samples are shown in 
Tables 1, 2, 3, and 4. The figures in all cases refer to the per cent of 
chlorine in dry fish. In Table 1 the analyses of sections of fish salted 
with a salt so prepared as to contain 1 per cent of calcium chloride 
and analyses of sections of similar squeteague salted with pure salt at 
the same time under identical conditions are presented. 

Table 1. — Retardation of Penetration of Salt into Fish Dxte to 1 Per Cent 
OF Calcium Chloride Impurity, Eixpressed in Terms of Per Cent of 
Chlorine in Dry Sample, at 62.-5° F. 



Analysis of salt used. 


Section of fish. 


Per cent chlorine after — 


Iday. 


i days. 


7 days. 


10 days. 


Pure sodium chloride 


Outer a 


9.8 
2.6 
8.7 

2.5 


16.2 
11.0 
10.8 

7.9 


19.6 
16.0 
15.2 

14.1 


19.5 


Do 




18.7 


1 per cent calcium chloride, 99 per cent sodium 
chloride. 

Do 


Outer o 


16.6 




14.4 










a to J cm. 


b§to 


1 cm. 









It is to be noted that the sections, both innei* and outer, of the fish 
salted with pure salt ran higher in chlorine content than those salted 
with salt containing 1 per cent of calcium chloride. 

In Table 2 data are presented which Avere obtained from the salt- 
ing of another lot of squeteague with pure salt and from a similar 
lot salted with salt so prepared that it contained 1 per cent of mag- 
nesium chloride impurity. 



24 



THE SALTING OF FISH. 



Tabke 2.— Rktardation of Penetration or Sai.t into Fish " Due to t Per Cent 
OF Magnesium Chloride Impurity, Expressed in Per Cent of Chlorine in 
Dry Sample, at 68° F. 



Analysis of salt used. 


Per cent chlorine after— 


1 day. 


3 days. 


ti days. 


9 days. 


Pure sodium chloride 


9.8 
6.5 


16.0 
15.7 


19 7 22 4 


1 per cent magnesium chloride, 99 per cent sodium chloride 


18.7 19! 



a Inner section of fish, J to 1 cm. 

In this ease, also, the chlorine content of the inner sections of fish 
salterl with pure salt is higher than that of similar sections of fish 
salted with the salt containing 1 per cent of magnesium chloride. 

Table 3 shows that an increase in the amount of magnesium chlo- 
ride to 4.7 per cent caused a further retardation. 

Table 3. — Retardation of Penetration of Salt into Fish Due to 4.7 Per 
Cent of Magne.stltm Chloride Impurity, Expressed in Per Cent of Chlorine 
IN Dry Sample, at 68° F. 



Analysis of .salt used. 


Section of fish. 


Per cent chlorine after— 


1 day. 


3 days. 


6 days. 


9 days. 


Pure sodium chloride 


Outer 


14.6 
9.8 
10.1 

5.9 


19.0 
16.0 
17.1 

12.7 


22.7 


22.7 


Do 


Inner 6 

Outer o 

Inner t> 


19.7 


22 4 


4.7 per cpnt magnesium chloride, 95.4 per cent 
sodium chloride. 
Do 


17.8 
17.1 


18.1 
18.1 


a Oto i cm. 




bito-i 


cm. 







Table 4 shows that the presence of the sulphate ion in solution 
caused a greater retardation than the consequent lowering of the con- 
centration of the chlorine ion should cause. 

Table 4. — Retardation of I'kxetration of S.^lt into Fish " Due to 10 Per 
('ent of Sodium Sulphate Impurity, Expressed in Per Cent of Chlorine in 
Dry Sample, at 68° F. 



Analysis of salt u.sed. 


Per cent chlorine after — 


Iday. 


3 days. 


6 days. 


9 days. 


Pure sodium chloride 


9.8 


16.0 


19.7 
15.3 


22.4 


10 per cent sodium sulphate, 90 per cent sodium chloride 


7.1 


10.5 


17.1 



a Inner section of fish, J to 1 cm. 

Further than a retardation of the rate of penetration of the sodium 
chloride, calcium chloride and magnesium chloride had noticeable 
effects on the i)hysical appearance of the salted fi.sh. Both the cal- 
cium chloride and magnesium chloride as impurities in salt made a 
mucli harder fish than pure sodium chloride. Calcium cliloride, ap- 
parently, was most active in this regard. Pure sodium chloride, 
when used dry for sahing fish, i)roduces a soft, yellow-meated fish 
which will bend when hold in the hand. Five per cent of calcium 



THE SALTING OF FISH. 



25 



chloride as impurity is sufficient to produce a very stiff, hard fish. 
One per cent of calcium chloride produced a softer fish, but yet one 
which was much harder than that produced by pure sodium chloride. 
Four and seven-tenths per cent of magnesium chloride, as impurity, 
produced a fairly hard, stiff fish, with a very bright, shiny appear- 



ance. 



Both calcium chloride and magnesium chloride, as impurities in 
salt, caused a very noticeable whitening. This whitening could easily 





























































^ 
















^fAii 


r* 


,c' 












y 




y\J* 




















/ 




rV\- 














/ 


/ 
/ 


i" 


[/»' 












/ 


^ 


<^' 


r 














^ 


^^ 


Y 














/ 


/ 
















/ 


/ 


















/ 





















22 

20 

18 

16 

14 

12 

10 

8 

6 

4 

2 



12 3 4 56 78 9 10 

Fig. 1. — Curves show retardation of penetration of salt due to 1 per cent of calcium 
chloride impurity (section | to 1 cm. depth). Figures at left indicate per cent of 
chlorine in dry fish ; at bottom, time in days. 

be followed, as it was first observed in the outer portions of the fish 
and moved toward the center until at the end of from 10 to 13 days 
the fish was uniformly white throughout. Calcium chloride was 
most active in this regard. 

Figures 1 to 4 illustrate graphically the data presented in the 
tables. In each case the time in days is plotted along the ordinate 
(horizontal line). The percentage of chlorine in the dry fish is 
plotted along the abscissa (vertical line). 

Figure 1 shows how the percentage of chlorine in fish (the amount 
of sodium chloride contained in the fish) increases for 10 days. The 
148957°— 20 i 



26 



THE SAI.TTXG OF FISK. 



salts used were pure sodium chloride in one case and sodium chloride 
containing 1 per cent of calcium chloride in the other. It will be 
noted that after seven days the chlorine content of the fish salted 
with pure salt is nearly 2 per cent liigher than that of the fish salted 
with salt containing 1 per cent of calcium chloride. The chlorine 
content of -the fish salted with pure sodium chloride continues to in- 
crease rapidly, whereas the chlorine content of the squetoairuo salted 



22 
20 
18 
16 
14 
12 
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Fxs. 2. 



s. 2. — Curves show retardation of penetration of salt due to 1 per cent of magnesium 
chloride impuiity (section J to 1 cm. deptli). P'igures at left indicate per cent of 
chlorine in dry fish ; at bottom, time in days. 

with salt containing calcium chloride increases \^vy much more 
slowly. 

Figures 2 and 3 show that the marked slowing up in the penetra- 
tion of the salt into fish, due to the presence of magnesium chloride, 
begins in about six days after salting. 

Figure 4 shows that the marked slowing up of the penetration of 
the salt into fish in the case of salt adulterated with 10 per cent of 
sodium sulphate occurs ahnost iiumediately. The amount of im- 
purity used in this case was far in excess of any amount ever found 
in anv commercial salt. It is doubtful whether small amounts of 



THE SALTING OF FISH. 



27 



sulphates found in commercial salts would have any appreciable 
effect on the penetration of salt in fish. 



SUMMARY. 



1. Small amounts of calcium chloride or magnesium chloride, as 
impurities in salt, retard the penetration of the sodium chloride into 
the squeteague. 



22 
20 
18 
16 
14 
12 
10 




































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^ 














L^ 


r 
















/^ 


,(!> 


y\\ 


f 












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y/ 


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/ 


/ 


















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1 


















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1 2 3 4 5 6 7 S 9 10 

Pig. 3. — Curves show retardation of penetration of salt due to 4.7 per cent of magnesium 
chloride impurity (section one-half to 1 cm. depth). Figures at left indicate per cent 
of chlorine in dry fish ; at bottom, time in days. 

•1. The sulphate ion has a similar, though less noticeable, effect. 
3. Calcium chloride and magnesium chloride, as impurities in salt, 
cause a firmer, whiter fish than pure sodium chloride. 

INFLUENCE OF IMPURITIES OX RATE OF PROTEIN DECOMPOSITION." 

INTRODUCTION. 

When the consideration of obtaining the relative values of different 
methods of salting fish was first taken up, the rate ,of penetration of 



" The analytical work reported in this section of the paper was done by .1. F. Steplil, 
temporary a.ssistant, U. S. Bureau of Fisheries. 



28 



THE SALTING OF FISH. 



chlorine into the fish was chosen as a criterion. The writer realized, 
however, that this alone was hardly a satisfactory criterion. Even 
if the salt penetrates fish with equal rapidity, it is no proof that the 
fish are keepin<r equally well. Different moisture contents would 
cause unequal keeping- qualities; also, some impurities in the salt 
might have a ori-enter jiresenative action than sodium chloride. 





















1 




on 














ytii 


^' 


fci 




18 










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Ifi 








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1 2 n 1 r. (i 7 s 9 JO 

Fig. 4. — Curves show retardation of penetration of salt due to 10 per cent of sodium 
sulphate impuritj' (section one-half to 1 cm. depth). Figures at left indicate i>er cent 
of cliloi-ine in dry fish ; at hottom, time in <iays. 

It was considered essential to have some means of measuring the 
amount and rate of decomposition of protein in order to judge as to 
how nuich decompositi(m took place while any given lot of fish was 
being salted. If the amount of decomj^osition at the end of the salt- 
ing process were known, the real value of any salting method as a 
means of preserving fish would be known. 

Wlieii proteins decompose, they bi'eak up. first, into simpler pro- 
teins, then into polyi)epti(ls. and then into amino acids. It is very 
difficult to measure accurately the amounts of simpler proteins and 
polypeptids in fish. However, the total amino-acid content of fish 
and brine is easily determined. 



THE SALTING OF FISH. 29 

A number of experimenters hare found that the amount of ammo 
acid formed is an index of the total protein de-composition in meat 
and fish. Hoagland, McBryde, and PoAvicii: (1917), working on the 
decomposition of beef during cold storage, found that the amino- 
acid content of beef increased relatively more than any other con- 
stituent. They found that the amount of amino acid formed varied 
directly with the length of the storage period. They say : 

The increases in amino nitrogen represent an accumulation of the end prod- 
ucts of proteolysis and furnisli an excellent index of the extent of protein 
autolysis. They are produced by the combined action of various proteolytic 
enzymes — protease and erepsin in particular — upon muscle proteins and their 
cleavage products. * * * 

Amino nitrogen showed greater actual and relative changes than any other 
nitrogenous constituent. This result was to have been expected, since this 
<'onstituent represents, in n large degree, an accumulation of the end products 
of proteolysis. 

Bradley and Taylor (1917) used the estimation of amino acids by 
the formol-titration method to measure the rate of digestion of pro- 
teins. 

Ottolenghi (1913) found that the amino-acid nitrogen content of 
meat was the best index of decomposition of meats. He used the 
amino-acid content to trace the ripening of meat to ascertain when 
active decomposition sets iu. He found that only Sorensen's formol- 
titration method for determining amino-acid nitrogen and the micro- 
scopic examination for bacteiia were of practical use for his purpose. 
Other methods were found to require too much time and elaborate 
manipulation. 

METHODS. 

Determination of amino-uHd nitrogen. — It was necessary to use a 
method of estimating amino-acid nitrogen which did not require a 
complicated apparatus. The procedure had to be short, so that a 
large number of analyses could be made in a day. The formol-titra- 
tion method is the only one that fulfills these requirements. There- 
fore, the amino-acid nitrogen was estimated in all cases by Sorensen's 
formol-titration method as modified by Benedict and Murlin. 

The writer is well aware that this method is open to many objec- 
tions. There are many slight errors due to the loss of diamino acids 
by precipitation, the high results given by some amino acids, and 
the low results given by others, etc. But for use as a measure of de- 
composition of protein a method does not need necessarilj^^ to give the 
exact amount of amino-acid nitrogen present in the fish or brine. If 
it gives results which are relative in all cases, it is sufficiently ac- 
curate for use where the results are used as an index of decomposition. 

The procedure in the detei-mination of amino-acid nitrogen in 
pickle was as follows : Twenty-five c. c. of brine were measured into 
a beaker. A quantity of 10 per cent phosphotungstic acid in 2 per 
cent hydrochloric acid, sufficient to precipitate all the protein, was 
added. This was allowed to stand overnight. The solution w^as then 
filtered and the precipitate washed. One c. c. of a 0.5 per cent solu- 
tion of phenolphthalein was added and barium hydrate in substance 
until the solution turned a permanent red. After standing at least 
half an hour the solution was filtered and the precipitate washed. 
The solution was then neutralized with half-normal hydrochloric 



30 THE SALTING OF FISH. 

acid. Enough tentli-noniial sodium hydroxide was then added to 
turn the sohition very slightly pink. Then 10 c. c. of neutral 40 per 
cent formalin were added and the solution titrated with tenth-normal 
sodium hydroxide. A blank on the formalin was run and this sub- 
tracted or added, as the case might be. 

When the determination was made on the fish, the procedure was 
varied as follows : Sections were cut from four fish. These were cut 
into small pieces and mixed. Twenty-five grams of this mixture 
weie weighed out and then gi'ound in a mortar for 5 minutes* 
Twenty-fi^'e grams of salt were added, and the sample was washed 
out of the mortar. The sample was then made up to 250 c. c. volume 
and was allowed to stand on ice overnight ; then sufficient was filtered 
off through a dry filter to obtain a 50 c. c. sample which was treated 
as in the case of the brine. 

Before sampling the salt the residual salt was thoroughly mixed 
after draining off the brine. A 25-gram sample was then weighed 
out. After dissolving the salt in water sufficient phosphotungstic 
acid was added to precipitate the protein and ammonia present. 
From this point the procedure was the same as for the brine and 
fish. In every case, after precipitation with phosphotungstic acid, 
the supei-natant liquid was tested to see if enough phosphotungstic 
acid had been added. 

Sdlt'inx/ of f^'^h. — Great emphasis was placed on uniformity of 
procedure throughout this experimental work. The experiments 
concerning protein decomposition as affected by the impurities in 
salt were carried out on river herring caught in the Albemarle 
Sound. These fish were purchased from fishermen and were iced as 
soon as they were brought ashore. This was about 1| hours after 
capture. They were then immediately cleaned thoroughly. The 
following procedure was followed in salting lots numbered FA-1, 
FA-4, FA-5, and FA-6. These results are reported in Table 5, 
page 32. 

The heads and all viscera were removed and the fish split along 
the belly to the vent. They were then soaked in ice water for an 
hour. The under side of the backbone was scraped free from blood, 
and all blood was washed out. The fish were then drained free from 
water, weighed, and salted. The river herring were rolled in salt 
and packed tightly, belly up. in layers in kits. Some salt was 
sprinkled over each layer of fish. No brine was added ; the fish de- 
veloped their own pickle. When packed, a weight of salt equal to 
one-third the weight of the fish was added. The following day a 
weight of salt equal to one-twelfth the weight of the fish was added. 

The salt used was either the commercial brand of salt known as 
Diamond Flake, or mixtures of this salt with chemically pure salts 
of similar degrees of fineness. Diamond Flake salt is a fine-grained 
salt prepared in Michigan, the analysis of which is given on page 18, 

Previously, an experiment had been run to determine whether the 
impurities present in commercial Diamond Flake salt were of suffi- 
cient importan(;e to cause a variation in its i^reservative action on 
fish from that of chemically pure sodium chloride taken as a stand- 
ard. The i-csult of this work showed that tlie differences in the 
amounts of amino-acid nitrogen formed in these two cases was 
within the limit of the experimental error. 



THE SALTING OF FISH. 31 

The kits of salted fish ^vere immediately phieed in a hii-fje, con- 
stant-temperature vat capable of holding seven small kits. The kits 
were held at a definite constant temperature throughout the salting 
period. In this case the temperature of lots FA-1, FA-i, FA-5, 
and FA-6 was held at 79° F. 

These large, constant-temperature vats were steel tanks. They 
were about half filled with water, which was electrically heated. 
A framework was built around them, and the space between the 
framework and the vats was filled with sawdust. They were fitted 
w ith wood covers and were also covered with paper and oilcloth. This 
effectually thermally insulated them. Hasselbring thermoregulators 
operated a relay system which regidated the operation of the heaters. 
A water motor drove the stirrers, which efficiently kept the vats at a 
uniform temperature tliroughout. In this experiment the tempera- 
ture did not vary more than 1° F. from the average, 

AnaJysis of fish. — Samples of the fresh fish were analyzed at the 
beginning of the experiment. It was found that uniformly cleaned, 
fresh alewives have practically the same amino-acid content. In the 
case of the well-cleaned and well-washed alewives this is about 0.02 
per cent amino-acid nitrogen (fresh basis). This fact might be 
utilized in judging freshness of fish. 

At the end of the experiment the fish, brine, and salt were weighed 
and sampled. The samples were analyzed for amino-acid nitrogen, 
according to the method described. The total weights of amino-acid 
nitrogen in the brine, residual salt, and fish were calculated. These 
were added together, and the total weight of amino-acid nitrogen 
contained in the fresh fish subtracted from their sum. This gave the 
total weight of amino-acid nitrogen formed. This figure was divided 
b}^ the original weight of the fish in kilograms. The result is the 
weight of the amino-acid nitrogen formed per kilogram of fish. 

This work is based on the supposition that the greater the decom- 
position of protein the greater will be the amount of amino-acid nitro- 
gen formed, inasmuch as the chief product of autolysis is amino- 
acid nitrogen. Where decomposition takes place so rapidly that the 
chief action is bacterial, amino-acid nitrogen is also formed; but in 
this case it is merely an intermediate product as the end products of 
bacterial action are ammonia and nitrogen. In such cases am- 
moniacal nitrogen ought also to be determined. The experimenter 
was always limited by lack of time arid facilities for elaborate 
chemical Avork. This is inevitable unless the investigator has the 
use of a complete chemical laboratory close to a large continuous 
supply of fresh fish and has the help of a corps of assistants. 

As long as there was but little spoilage of fish in the experiment, 
the results of the amino-acid determinations from different lots salted 
under identical conditions checked excellenth'. But when the spoil- 
age was great enough to cause the formation of foul-smelling gases 
and was quite evidently of a bacterial nature the amounts of amino- 
acid formed did not show what was anticipated. Surely, in such 
cases the ammoniacal nitrogen ought to have been determined. 

The results of the analyses and calculations are given in Table 5. 



32 



THE SALTING OF FISH. 



Tahle 5. — Effect of Calcium Chloride and Magnesium Chloride in Salt on 
Rate of Amino-Acid Foemation in Salted Fish." 



[Lots D refer to samples dry-salted, and lots S to those brine-salted.] 



Lot No. 



FA-LD. 



rA-4:D. 



FA-5:D. 



FA-6: 
DA-8: 



DA-9:S. 



Method of 
cleaning. 



Heads removed; 
eviscerated; well 
washed. 



-do. 



.do. 



do 

Heads removed; 
eviscerated with 
exeeptionofmilt 
and roe. 

.-..do 



Analysis of 
salt. 



Per cent. 

5.0 calcium chlo- 
ride; 0.37 cal- 
cium sulphate; 
9-1. 7S sodium 
chloride. 

5.0 magnesium 
chloride; 0.37 
calcium sul- 
phate; 9-1. 78 so- 
dium chloride. . . 

99.78 sodium chlo- 
ride, Diamond 
Flake. 

do 



.do. 



94. 7S sodium chlo- 
ride; 5.0 sodium 
sulphate; 0.37 
calcium sul- 
phate. 



Weight 

of salt 

and 

brine 

used. 



Kgs. 



C1.2.J 

b6, n 



b(i, n 



Salting period. 



Aver- 
age 
tem- 
pera- 
ture. 



79 



Length, 



Days. 



Weight 

of 

fresh 

fish. 



Gra ins. 
4,000 



3,000 



3,000 



3,000 
5,000 



5,000 



Ami no-acid 
nitrogen in 
fresh fish. 



Per ct. 
002 



.02 



.02 



.02 
.022 



.022 



Oramt. 
0.89 



. r,o 



.60 



.(iO 
1.10 



1.10 



Lot No. 



Total 


imino-acid nitrogen at 
end in— 


Amino-aci(i 
nitrogen 
formed. 


Fish. 


Brine. 


Salt. 


Fish, 

brine, 

and 

salt. 


Total. 


Per 
kilo- 
gram 
fresh 
fish. 


Grams. 


Grams. 


Grams. 


Grams. 


Grams. 


Grams. 


2.20 


0.53 


0.07 


2.80 


2.00 


0.500 


1.17 


.52 


.05 


1.74 


1.14 


.380 


1.00 


.50 


.07 


1.57 


.97 


.323 


1.07 


.48 


.06 


1.61 


1.01 


.336 


2.46 


2.09 


None. 


4.55 


3.45 


.69 


2.82 


1.97 


None. 


4.79 


3.69 


.74 



Physical condition of salted fish. 



FA-1:D. 
FA-4:D. 
FA-5:D. 
FA-6:D. 
DA-8:S.. 
DA-9.S.. 



Good; hard; whitened. 

Do. 
f^rood; hard; yellow-white. 

Do. 
Contained 2 bad fi.sh: total number, 2.'> 
Contained 3 bad fish; total number, 25 



a The fish in this experiment were salted four hours after capture. 



b Brine. 



Salt. 



discussion. 



Effect of calcium and jiiagiiesiuin salts. — It should be note^I that 
the amounts of impurities, calcium, magnesium, and sodium sulphate 
that were added are great. The combined amounts of calcium and 
magnesium salts occurring in commercial salts is seldom over 4 per 
cent. The analyses given on pages 18 and 19 show the composition of 
various commercial salts. 

More aniino-acid nitrogen was formed in lot FA-1 than in lots 
FA-4, FA-f). or FA-6. Lots DA-8 and DA-9 were cleaned in a 
different manner and were salted in brine instead of dry salt ; sotliese 
results are not comparable with the results of the lots numbered FA. 



THE SALTIXG OF FISH. 33 

'Lot FA-l was salted with salt containing calcium chloride as im- 
pnrity. This increase in the amount of amino-acid nitrogen formed 
was about 50 per cent OAer the weioht of amino-acid nitro<jen formed 
when pure salt was used. In other words, there was a half more 
decomposition of the protein when the salt contained o pei- cent of 
the calcium chloride than when no calcium chloride was present. 
Five per cent of calcium chloride is only the equivalent of 1.8 per 
cent of calcium. This is a o^reater amount than was contained in 
any whose analyses are ^ven in the tables of salt analyses. 

Salt sample number MD lfilO'2 contained 1.33 per cent calcium. 
However, it will be noted that the total impurity amounted to 7.3 
per cent. Lot FA-4 was salted with salt containing* 5 per cent of 
magnesium chloride. In this case 0.380 gram of amino-acid nitrogen 
was formed during the salting period. This is 15 per cent more than 
when pure salt was used (FA-5, FA-6). However, 5 per cent of 
magnesium chloride is 1.28 per cent of magnesium, which is double 
the amount of magnesium likely to be found in any commercial salt. 

If the salt analyses given previously are consulted, it will be seen 
that the Trapnni salt sample is the only one that contains a very large 
amount of magnesium and that this amount is less than 3 per cent 
of total magfuesium salts. It seems unlikely, therefore, that the 
amounts of magnesium salts contained in commercial salts have any 
appreciable deleterious effect on the fish-curing properties of any 
salt. 

Efect of sodiu7n, stdfhate. — Samples DA-8 and DA-9 were pre- 
pared for salting by cutting off the heads and cutting" the length of 
the abdominal cavity. All viscera were removed with the exception 
of the milt or roe. As the milt and roe were left in the fish, it was 
impossible to wash the fish thoroughly, or to remove all the blood. 
For this reason the maximum temperature of salting was greatly 
lowered, even though all other conditions were identical. These fish 
were salted in brine. For every gram of fish taken 1 c. c. of brine 
was used. At the time of salting a considerable excess of solid salt 
was added. From time to time more solid salt was added. The fish 
were stirred daily. Sufficient salt was added to keep the pickle sat- 
urated at all times. The amount of salt required for this purpose was 
about one-fifth of a gram of salt for every gram of fish. 

The samples were taken at the end of the salting period. They were 
analyzed, and the calculations were made in the manner previously 
described. Lot DA-8 was salted with nearly pure salt. The salt 
used in lot DA-9 contained 5 per cent sodium sulphate as impurity. 
These lots were salted just above the maximum temperature for fish 
cleaned in this way (containing roe, milt, and blood). Any differ- 
ences in the preserving or penetrating powers of the salts used should 
show up very noticeablv under these conditions. Yet there is only a 
difference of 7 per cent in the amount of amino-acid nitrogen formed. 
There is a little more decomposition in the case of the salt containing 
the sodium sulphate, but the difference is slight. There is usually 
not more than 2 per cent of sulphates contained in commercial salts. 
Had the amount of sodium sulphate been reduced to 2 per cent it is 
likely that the difference between the preservative power of the im- 
pure salt and the pure salt would have hardly been noticeable. 



34 THE SALTING OF FISH. 

These results concerning the rate of formation of aniino-acid 
nitrogen check with those on the penetration of chlorides; that is, 
where there was a slowing up in the rate of penetration of chlorides, 
there is an increase in the rate of amino-acid formation. The 
changes are approximately the same, except in the case of the effect 
of the sulphates. The results obtained from the work on rate of 
penetration of salt adulterated with sodium sulphate show a marked 
decrease in the rate of penetration, due to the impurity. The in- 
crease in rate of production of amino acids due to the presence of tliis 
impurity is very slight. However, the work on the rate of penetra- 
tion was done with salts containing 10 per cent of sodium sulphate. 
It may be that this marked retardation takes place only at high con- 
centrations of sodium sulphate, when there is a marked hardening 
of the tissues. 

DISCUSSION- 
PHYSICAL EFFECTS ON FISH. 

This work on the preservative action of different salts was done on 
alewives, whereas the penetration of salts were followed in sque- 
teagues. The hardening and whitening action of calcium and mag- 
nesium salts was marked on alewives; but it was less noticeable than 
in the case of squeteagues. Five per cent of sodium sulphate had 
practically no whitening action on alewives and very little hardening 
action. It may be that 10 per cent of sodium sulphate in salt is 
required to bring out the whitening power. No lot of alewives was 
salted with salt containing more than 5 per cent of sodium sulphate. 

A POSSIBLE EXPLANATION OF RESULTS. 

The writer believes that the hardening action of calcium and mag- 
nesium salts on the tissues of the fish is responsible for the retardation 
of the penetration of the chlorides. This, in turn, is at least partially 
responsible for the lesser preservative action of the impure salts. 
Sodium sulphate evidently acts only when in greater concentrations 
than it is ordinarily found in conunercial salts. Its deleterious action 
as an impurity is, therefore, not to be feared. 

I'RACTICAL AITLICATION. 

When fish are salted at any temperature averaging below .50° F., 
salts may be chosen that will produce the desired quality of salted 
fish. When a hard, white fish is desired, salts high in calcium and 
magnesium salts may wisely be chosen. However, if a soft, pliable 
fish is desired, pure salts should be used. 

When the average temperature of salting is above 50° F., greater 
care should be used in the selection of salt. This becomes of par- 
ticular importance when the fish are salted, either round or contain- 
ing blood, roe, or milt, as these fish are much more likely to spoil than 
when they are thoroughly cleaned. In this case the smaller the 
amounts of calcium and magnesium salts present the more desirable 
the salt. Fish salters working in warm climates should strive to 
obtain salt containing less than 1 per cent of total calcium and mag- 
nesium salts. Su]i)hates are never present in lai-ge enough quanti- 
ties to lower the effectiveness of the salt as a preservative. 



THE SALTING OF FISH. 36 

EKFKCT OF FINENESS OF SALT. 

The writer considered the fineness of salt as of little importance, 
save in a physical way. Inasmuch as his time was limited, he con- 
ducted no experiments to determine the optimum degi'ee of fineness 
of salt for use in fish salting. This factor is entirely eliminated 
when fish are salted by the brine method. When small fish are salted 
with dry salt, care must be taken not to use too coarse a salt, such as 
Turks Island. When such a coarse salt is u- ed, gi'eat difficulty will 
be encountei'ed in obtaining a uniform distribution of the salt 
throughout the barrel or butt of fish. Nearly all of the salt used Avill 
be on the outside of the fish. If, hoAvever, fine salt be used, a con- 
siderable portion of the salt will be inside the abdominal cavity. 
This abdominal cavity usually is quite moist; so almost immediately 
a strong pickle will be formed which will begin to penetrate the fish. 
Fine salt certainly has the advantage of being easier to distribute 
evenly throughout a container of fish regardless of the size of the 
fish. However, in the case of cod and other large fish fine salt gives 
the fish a somewhat different apj^earance. In such cases, when the 
Aveather is cold, appearance should be the first consideration. If 
such large fish are salted in warm, southern climates, less considera- 
tion can be given to the appearance of the product. In such cli- 
mates the first considerations must be the composition of the salt and 
its uniform distribution throughout the container of fish. 

SUMMARY. 

C'alcium and magnesium salts and various sulphates cause a re- 
tardation of the penetration of salt into fish. These salts also cause 
a less perfect preservation of the fish during salting. This was 
shown by increased amounts of amino acids formed during the salt- 
ing period. Calcium is most powerfid in this regard. Magnesium 
salts cause a considerable increase in the rate of decomposition dur- 
ing salting, other conditions being the same. But this effect is not 
nearly so great as that caused by calcium salts. Sulphates do not 
cause an appreciable increase in the rate of decomposition at the 
concentrations at which they are present in salt. The fish Salter 
working under adverse conditions in warm climates should use care 
in the selection of his salts and choose salts that are low in calcium 
and magnesium. 

II. A COMPARISON OF EFFICIENCY OF BRINE AND DRY SALT FOR 

SALTING FISH. 

IM TRODUCTION. 

At present fish are salted either by the use of dry salt or brine 
and salt. Before improvements in either method could be suggested 
it was considered essential to know the relative merits of the two 
methods at various temperatures. The work presented in this sec- 
tion of this paper was undertaken, therefore, with that aim in view. 

The dry-salt method invoh^es the packing of fish with salt in a 
water-tight container. The water and body juices of the fish dis- 
solves sufficient salt to make enough "pickle " to cover the fish. A 
small pile of salt is usually placed on top of the container to press 



36 THE SALTING OF FISH. 

down the fish and keep them covered. The fish are not*disturbed 
until the end of the salting period. 

In the brine method of salting fish the procedure is as follows: 
Fish are dumped into a vat containing enough brine nearly to cover 
them, and a considerable quantity of rait is added along with the 
fish. Each day more salt is added, and the fish are stirred in the 
"pickle.'' The purpose of adding the salt is to maintain the brine 
as near saturation as possible. 

In these experiments these two methods were given a trial. The 
commercial methods were imitated as closely as possible in order to 
fairly compare the methods. 

DETERMINATION OF RATES OF PROTEIN DECOMPOSITION. 



Ninety pounds of reasonably fresh squeteague (Cynoscion regalis) 
were obtained. The fish had been caught two days previously and 
had been kept on ice. There were 120 fish in all, making the aver- 
age weight three-fourths of a pound. They were cut down the 
belly and eviscerated. The tails and heads were cut off, and the 
fish were washed in ice water. 

After cleaning there remained 23.4 kg. of fish. These were divided 
into 12 lots. Six lots of 1.3 kg. each and six other lots containing 
2.6 kg. each were weighed out. To each of the smaller lots were 
added 1,300 c. c. of saturated sodium chloride solution and 250 
grams of pure, dry sodium chloride. The fish of the larger lots 
were rubbed in chemically pure dry salt and then packed in 
glass dishes, cut surface down, and sodium chloride was sprinkled 
over each layer. The 2.6 keg of fish just made two layers; 990 
grams of salt were used in this way on each lot. The salt used in 
this experiment was chemically pure " Baker's analyzed " sodium 
chloride. This salt is a little smaller grained than " ground alum." 

One of each of the lots of fish was then placed in a different con- 
stant-temperature compartment. The fish were permitted to remain 
in this constant-temperature apparatus for nine days. The brine- 
salted lots of fish were stirred daily. The temperature in any one 
compartment did not vary more than 1° F. from the average. The 
brines were sampled and analyzed for amino-acid nitrogen on the 
first, third, fifth, seventh, and ninth days. At the end of the experi- 
ment the fish and salt were also analyzed for amino-acid nitrogen. 
In the case of fish to which the brine had been added not more than 
25 grams of salt remained undissolved. The amount of amino-acid 
nitrogen in this small amount of salt was considered negligible. In 
all cases, however, there was an excess of undissolved salt at the end 
of the salting period. 

The method of sampling the fish, brine, and salt was described 
in the first section of this paper. The method of analysis of the 
samples for amino-acid nitrogen was the formol -titration method, 
which was described on page 29. 

DiscrrssioN. 

Table 6 shows the titration values obtained by the formol titration 
for amino acids of 25 c. c. of the brines. These figures are given 



THE SALTI^^G OF FISH. 



37 



to show the rate at which the amino acid diffuses out into the brine. 
They also point out a means of forecasting spoilage of fish. 

TABiJi; 6. — Increakk ix Amino- Acid Tontent of Brines. 

IFigui-es refer to c. c. N/'IO NaOH amino acid coiitaine<l in 25 e. c. of brine : Lots D 
refer to samples dry salted ; lots S, to those brine salted. ] 



Lot. 






Brine collected after— 




19 
hours. 


67 
hours. 


5 days. 


7 days. 


9 days. 


C. c. 


C.c. 


C.c. 


C.c. 


C.c. 


4.7 


5.0 


5.1 


5.1 


6.5 


1.3 


2.0 


2.1 


2.7 


3.4 


4.7 


4.9 


5.6 


5.4 


7.1 


1.4 


2.4 


2.3 


2.7 


4.2 


4.4 


5.2 


5.7 


5.9 


7.6 


1.4 


2.6 


2.5 


3.2 


4.4 


4.4 


5.1 


7.0 


7.6 


8.5 


1.2 


2.7 


3.0 


4.2 


«5.3 


4.1 


4.8 


8.7 


a 9. 6 


alO. 1 


1.3 


3.4 


3.7 


o5. 2 


a 7. 2 


4.4 


7.2 


O10.3 


O13.0 


a 16. 


1.1 


3.4 


ffl4.6 


o 6. 6 


«9.5 



Tem- 
pei- 
atiirp. 



'F. 
03 

70 
70 

75.5 
75. 5 

80 

HO 

8" 
87 

'.n 
'■r.i 



o Spoilage of fish noted. 

Apparently the water contained in the fish diffuses out more rap- 
idly in the case of the drj'-salted fish. Above 86° F. sufficient brine 
to cover the fish was formed from the dry salt in 15 hours. About 30 
hours were required for the lots at 70 and 63° F. to form enough 
brine to cover all the fish. The lots at 75.5 and 80° F. formed suf- 
ficient brine to cover the fish in somewhat less time. The gradual 
increase in the amino-acid content of the brines of the brine-salted 
fish (S) was probably due to the slow diffusion out of the water con- 
taining the amino acids dissolved in it. The immediate rise of the 
amino-acid titration value to about 4.5 c. c. in the dry-salt method 
was probably due to the rapid movement outward of the water in 
the fish. 

When the amino-acid titration values rose above 9 c. c. in the dry- 
salted lots, the fish (D) were found to be spoiled. This was observed 
in five days at 93° F. and in seven days at 87° F. The lot at 80° F. 
did not spoil in this case. 

In the case of those fish salted in brine (S) when the formol-titra- 
tion value rose to 5 c. c. N/10 alkali, the fish were observed to be 
spoiled. This was noted at five days for those at 93° F. ; at seven 
days for those at 87° F. : and at nine days for those at 80° F. 

Table 7. — Voli'me.s of Brine Formed During Salting. 
[Lots D refer to samples dry salted; lots S, to those brine salted.] 



L«^. 


Weight 
offish. 


Volume. 


Lot. 


Weight 
of fish. 


Vol- 
ume. 


2D 


Kg. 
2.6 
1.3 
2.6 
1.3 
2.6 


C.c. 

770 
1,580 

815 
1,610 

«20 


5D 


Kg. 
2.6 
1.3 
2.6 
1.3 
2.6 
1.3 


C.c. 

780 


2S 


5S 


1,625 


3D 


6D 


860 


3S 


6S 


1,670 


4D 


7D .. 


680 


4S 


1.3 1-670 


7S 


1,620 













38 



THE SALTING OF FISH. 



The figures in Table G, togetlier with the volumes of*the brine 
given in Table 7, were used to calculate the total amounts of aniino- 
acid nitrogen formed in the brines. These figures are given in 
Table 8. 



T.\Bi,E 8. — Total Amount of Amino-Acid Nitrogen Formed in Brines. 
[Lots D refer to samples dry salted; lots S, to those brine salted.] 







Total amount 


amino nitrogen after 


- 


Temper- 
ature. 


Lot. 


19 hours.' 


67 hours. 


5 days. 


7 day.s. 


9 days. 




rD 


Grams. 
0.203 
.115 
.217 
.130 
.201 
.1.33 
.192 
.112 
.197 
.126 
.168 
.104 


Grams. 
0.215 
.168 
.224 
.215 
.238 
.242 
.222 
.246 
.230 
.317 
.273 
.310 


Grams. 
0.220 
.176 
.254 
.205 
.259 
.233 
.310 
.273 
.414 
.345 
.392 
.417 


Grams. 
0.220 
.238 
.250 
.247 
.270 
.298 
.367 
.392 
.505 
.488 
.499 
.602 


Grams. 
0.311 
.304 
.328 
.380 
.349 
.412 
.412 
.498 
.532 
.677 
.614 
.867 


°F. 
63 


^■ 


s ... 


(i3 




\d: 


70 


^ 


s 


70 




[d : ;: 


75.5 


4. 


s 


75.5 




^D 


80 


^ 


S 


80 




^D 


87 




S 


87 


.. 


D..: 


93 


'• 


[S. . 


93 













In order to make the figures in Table 8 comparable, the total 
amounts of amino-acid nitrogen formed were divided by the weights 
of fish salted in the different lots. These figures are presented in 
Table 9. 

Table 9. — Amount" of Amino-acid ISitrouen Formed in Brine per Kilogram 

OF Fish. 

[Lots T> refer to samples dry salted: lots S, to those brine salted.] 





Amino-aoid nitrogen per kilogram of fish after— 




Lot. 




Temper- 












ature. 




19 hours. 


67 hours. 


5 days. 


7 days. 


9 days. 






Grows. 


Grams. 


Grams. 


Grams. 


Grams. 


"¥. 


. 


D 


0.078 
.089 
.084 


0.083 
.129 
.086 


0.085 
.135 
.098 


0.085 

.183 
.097 


0.119 
.234 
.126 


63 


^ 


S 


63 


o 


D 


70 


* 


S 


.100 


.165 


.158 


.190 


.292 


70 


il 


D 


.077 


.092 


.099 


.104 


.134 


75.5 


i 


S 


.102 


. 186 


.179 


.228 


.316 


75.5 




D 


.074 


.086 


.119 


.141 


.158 


80 




S 


.086 


.189 


.210 


.300 


.383 


80 


JT> 


.076 


.089 


.159 


.195 


.208 


87 


^S 


.097 


.244 


.266 


.377 


.510 


87 


7/D 

'\S 


.065 


.105 


.151 


.193 


.236 


93 


. 080 


.238 


.320 


.465 


.666 


93 



At the end of the experiment samples from each lot were cooked. 
All the fish salted at 87 and <)H° F. weiv spoihMl. About 20_ per 
cent of the fisli salted in brine at 80° F. were spoiled. None of the 
fish .salted by the dry-salt method at this temperature (80° F.) were 
spoiled. Fish salted with dry salt at 80° F. were eaten both by Prof. 
B. P. Livingston and the writer and Avere ]n'onounced satisfactory. 
All fish salted at lower temperatures were in good condition. The 
results of the cooking trials check with the amount of decoin])Osition, 
as shown by the total amount of amino acids formed in Table 10. 



THE SALTING OF FTSH. 



39 



A composite sample of the frosh squeteague gave on analysis 0.022 
per cent amino-acid nitrogen. This figure was found to be fairly 
constant for squeteagiies but was higher when the samples had been 
iced for a long period. 

In Table 10 the various amounts of amino-acid nitrogen formed in 
the bi'ine, fish, and salt are given; also the total amino-acid nitrogen 
formed and the total amount of amino-acid nitrogen formed per 
kilogram of fish is given. 

Table 10. — Total AMorxx ok Amino-Acid Is'itrogen Formed Dl^ring Salting 

Period." 

[Lots D refer to samples drj- salted : lots S, to those brine salted.] 



Lot. 



il 

^s 



Amount 
of salt 
used. 



Amount 

of brine 

used. 



Grams. 
990 
250 
990 
2o0 
990 
250 
990 
250 
990 
250 
990 
250 



C.c. 



1,300 

'i'soo' 



1,.300 

"i,"366' 



Average 
tempera- 
ture of 
salting. 
period. 



1,300 
'i.loo' 



F. 

63 
63 
70 
70 
75.5 
75.5 
80 
80 
87 
87 
93 
93 



Weight 

of 

fresh 

fish. 



Grams. 
2,600 
1,300 
2,600 
1,300 
2,600 
1,300 
2,600 
1,300 
2,600 
1,300 
2,600 
1,300 



Amino-acid nitro- 
gen in fresh 
fish. 



Per cent. 
0.022 
.022 
.022 
.022 
.022 
.022 
.022 
.022 
.022 
.022 
.022 
.022 



Grant t. 
0.572 
.286 
.572 
.286 
.572 
.286 
.572 
.286 
.512 
.286 
.572 
.286 



Total amino-acid nitrogen at 
end in — 



Amino-acid nitrogen 
formed. 



Lot. 



^s 

ii 

Is. 



Pish. 


Brine. 


Grams. 


Grams. 


0.660 


0.311 


.333 


..304 


.675 


.328 


.285 


.380 


.783 


.349 


.332 


.412 


6.934 


.412 


6.451 


.498 


61.276 


.532 


6.594 


.677 


61.492 


.614 


6 .610 


.867 



Salt. 



Fish, I 

brine, i rp-^„, 
and I '■°^^^- 
salt, i 



Grams. 
0.056 
.000 
.065 
.000 
.053 
.000 
.078 
.000 
.068 
.000 
.096 
.000 



Grams. 
1.027 

.637 
1.0K8 

.665 
1. 185 

.744 
1.424 

.949 
1.896 
1.271 
2.202 
1.477 



Grams. 

0.455 
.351 
.496 
.379 
.613 
.458 
.854 
.663 

1.324 
.985 

1.630 

1.191 



Per 

kilo- 
gram 
fresh 
fish. 



Grams. 
0.175 
.270 
.190 
.292 
.236 
.352 
.328 
.510 
.510 
.756 
.628 
.916 



In- 
crease 
over 
dry-salt 
meth- 
od. 



Per 
cent. 



Physical condi- 
tion of salted 
fish. 



Good. 

Do. 

Do. 

Do. 
Fair. 

Do. 

Do. 
Spoiled. 

Do. 

Do. 

Do. 

Do. 



a In this experiment the fish were cleaned after two days' iciog by removing the heads, eviscerating, and 
washing carefully, and were salted for nine days. 

6 Number is slightly high because of the accidental discard of the sample by one of the writer's coworkers. 
The result given is from sample taken three days after the fish had been removed from the constant- 
temperature compartments. The fish were kept at 64.5° F. during those three days. However, any slight 
error would be the same for all samples. 



These figures show that the total amounts of amino-acid nitrogen 
formed are much greater in the case of the brine-salted fish. The 
increase varies from 48 to 55 per cent. This seems to prove that 



40 



THE SALTITiJ^G OF FISH. 



the brine-salt method is not as efficient in preserving fish lis the dry- 
salt method. 

The writer wishes to point out the value of the amino-acid con- 
tent of fish and brine as a criterion in estimating and detecting 
spoilage. Any two lots of the same fish may be compared and their 
relative freshness determined. This may be used for either fresh 
'or salted fish. If the fish have been salted by the same process, this 
may be done quite easily hj determining amino-acid nitrogen in 
the brines. 

It also seems probable that the increase in amino-acid content 
could be used to forecast spoilage of fish during the salting period. 
A rapid rise in the amino-acid content of the brine would warn the 
Salter that his fish were in danger of spoiling, and the Salter could 
remove them to cold storage or use stronger brine. 

RATE or PENETRATION OF SALT. 

In addition to following the formation of amino-acid nitrogen in 
fish salted by these two ways, the rate of penetration of chlorides 
into squeteagues was followed. This was accomplished in the same 
manner as the determination of the rates of penetration of different 
salts described on page 22. 



The general procedure in these experiments was as follows: Fish 
of a uniform size (3.5 cm. thickness) were salted with pure sodium 
chloride by the tM-o methods described on page 36. These two jars of 
fish were placed in a constant-temperature compartment and sampled 
at the end of 1, 4, 7, and 10 days. The temperature of the fish did 
not vary more than 1.44° from the average of 69.44° F. The samples 
were dried and ashed and the chlorine determined by titration with a 
silver-nitrate solution. The results are given in Table 11. 

Table 11. — Penetration of Salt into Sqiteteagve, Expressed i.n Terms ok 
PER cent of Chlorine in Dry Sample, at 70° F. 





Method of salting. 




Section of fish. 


Per cent chlorine after— 




1 day. 


4 days. 


7 days. 


10 days. 




Outer 1 


9.8 
2.6 
8.4 
1.8 


16.2 
11.0 
15.3 
8.3 


19.6 
16.0 
17.3 
12.2 


19. .5 


Do 


Inner b 


18.7 




Outer 1 


17.8 


Do . 


Inner i> 


15.7 










o to i cm. 


DISCI 


t J to 1 cm 
•SSION. 











The percentage of salt in both sections is higher throughout in 
the case of the dry-salted fish than in the brine-salted fish. This 
shows that the salt penetrated mor-e rapidly in the case of the dry- 
salt method. More data could be given which verify the results 
of this experiment. 

Tliis work agrees with the results obtained by the estimation of 
the rate of amino-acid formation. For, when the salt penetrates 



THE SALTI]iG OF TISH, 



41 



more rapidly, as in the case of tlie dry-sail method, less amino acids 
are formed than when the salt penetrates more slowly. Ho^wever, 
the retardation of the rate of penetration is less marked. This sug- 
gests the possibility that small differences in salt content of fish may 
be responsible for much greater differences in the rate of decom- 
position of the fish. 

Figure 5 illustrates graphically the data given in Table 11. It 
should be noted that the difference in chlorine content gradually 
increases. 



22 
20 
18 
16 
14 
12 
10 







r 






















































^ 
















/^ 








, 








y 


^v 


f 


_^ 


^ 










/ 


0*^ 


> 


A 


X 










/ 


/ 


y 


<-' 


M*- 










/ 


/ 

> 


V 














4 


A 


/ 
















A 


/ 
















/. 


y 


















/ 





















3 



6 



10 



Ki«. n. — Curves show comparative rates of penetration of salt into fish when dry salted 
and when brine salted (section one-half to 1 cm. depth). Figures at left indicate per 
•eiit of chloride in dry fish ; at bottom, time in days. 



DI8CUSSIO> . 
PHYSICAL DIFFERENCES BETWEEN THE PRODUCTS OF THE TWO METHODS. 

Dry-salted fish are invariably harder than brine-salted fish. This 
is probably due to the difference in moisture content. Brine-salted 
fish are about 7 per cent higher in moisture than dry-salted fish at the 
end of a salting period of 10 days. Dealers who ''tight pack " their 
fish state that dry-salted fish require very little draining, whereas the 
brine-salted fish must be drained and dried for at least four days. 



42 THE SALTING OF FISH. 

Dry-salted fish have a shriveled appearance, due to their 3rier con- 
dition. They are also brip^hter in appearance, as a less number of 
scales haA^e been knocked off. 

HYPOTHESIS TO ACCOUNT FOB BEStTLTS. 

There are three important means of preserving foodstuffs, namely : 
1. By destruction of bacteria and enzymes, which is accomplished by 
sterilization with heat. 2. By desiccation, or removal of water ; bac- 
teria do not thrive, nor are enzymes active in the absence of water. 
3. By the addition of a preservative, which inhibits the growth of 
bacteria and the action of enzymes. 

When fish are jjreserved by salting, we make use of the two last- 
mentioned means of preservation. The salt not only penetrates the 
fish but also dissolves and removes water. In some way dry salt re- 
iTioved more water from fish than brine. In the case of the dry-salt 
method the salt content of the fish is greater. The lesser decomjjosi- 
tion taking place during dry salting than during brine salting is evi- 
dently due to these two facts. 

It is not clearly understood just why the salt penetrates more 
rapidly when the dry-salt method is used. After stirring a vat of 
fish which are being brine-salted, the concentration of the upper 
layers of pickle immediately begins to decrease. It decreases most 
i-apidly just after the fish are put in. In large vats of fish, the pickle 
sometimes becomes as weak as 60° (GO per cent saturation), even 
though there may be solid salt in the vat. Of course, this diluted 
brine is not so active as saturated brine. Also, it may happen that, 
although the pickle appears saturated according to the hydrometer 
reading, that in contact with the fish is not saturated, for water con- 
tinually comes out of the fish and dilutes the brine in the vicinity of 
the fish. It would be well to try an experiment comparing the brine- 
salting method with the dry-salt method and have both brines stirred 
continually. The writer believes that both methods would show up 
equally well in such a test. 

DRY-SALT METHOD MORE ECONOMICAL. 

The dry-salt method involves a little more work at the beginning 
of the salting period; for more labor is involved in thoroughly dis- 
tributing the salt throughout a large quantity of fish than is re- 
quired to make up a brine and i)ut the fish and salt into it. But after 
packing the fish into butts with dry salt, no further labor is required; 
wliereas, brine-salted fish must be "roused" (stirred up), and salt 
must be added every day during the salting period. " Eousing " is 
an operation that requires considerable time and labor, and since the 
fish must be roused eight or nine times, the total labor expended in 
this process is large. There is no reason, therefore, for the brining 
of fish in order to save labor, as in the long run this process is not 
economical in respect to labor. 

At present the used pickle from both processes is thrown away. It 
is the custom to save the surplus salt used in the dry-salt method. A 
great deal more pickle is left at the end in the brine method. This 
involves a greater loss of salt, when it is discarded, than when the 
smaller amount of dry-salt pickle is thrown away. The .dry-salt 



THE SAJLTING OF FISH. 43 

method is, therefore, more economical in regard to salt, as well as to 
labor. 

SUMMARY. 

1. The formation of amino-acid nitrogen was followed in the brine 
during- the salting of fish by two methods — salting by use of dry 
salts and salting by use of brine. 

2. The total amount of amino-acid nitrogen formed during salt- 
ing was calculated. 

3. More amino acid was formed by the brine method of salting. 

4. The estimation of the amino-acid nitrogen content of fish and 
brine was suggested as a means of detecting and also forecasting 
spoilage. 

5. The rate of penetration of salt into the squeteague when salted 
with dry salt and when salted with brine was determined. Salt 
applied dry goes into the fish more rapidly. 

6. Samples of the fish salted by the two methods under considwa- 
tion were cooked. It was found that all of the fish salted with dry 
salt at 80° F. were edible. Those salted with brine AA^ere unfit foV 
consumption. 

7. The dry-salt method was found to be more economical both of 
labor and salt. 

These results show that the dry-salt method of salting fish, as- 
practiced commercially, is much more efficient in preserA^ing fish than 
the brine method. The dry-salt method is also the nioro econoinical 
of the two. 

III. INFLUENCE OF METHOD OF CLEANING FISH FOR SALTING. 

INTRODTTmON. 

IMPORTANCE OF METHOn OF (TJOANING. 

It has always been known that the method of cleaning a fish pre- 
paratory for salting has an important influence on the quality of 
the product. From the first the Avriter noted that the salt penetrated 
more rapidly through the cut flesh of fish than through a surface 
coA-ered with skin. This was first noticed AA'hile following the pene- 
tration into the fish of salt containing calcium chloride. The cal- 
cium chloride produced a marked whitening of the tissue. This was 
obserA^ed to proceed more rapidly on the cut side of the fish than on 
the side covered with skin. 

The common practice in rating the quality of a salted herring or 
alewife is to break the fish open so that the backbone is exposed. 
The odor of the dark red or brown spots is then observed. The 
experienced fish Salter knows that these spots are the first parts of the 
fish to spoil. They are caused by the coagulation and partial de- 
composition of the blood. Most fish salters seem to realize that the 
blood is the most unstable substance contained in fish, for they rate 
the efficiency of different procedures in fish salting by the amount 
of blood that the processes " draw out." They are AvelJ aware of the 
fact that roinid fish can not be salted at as high "a temperature as cut 
fish. Numerous fishermen hn\e advi.sed theNvriter that verv little 



44 THE SALTING OF FISH. 

trouble would be encountered in salting any fish if care would bo 
taken to scrape the blood away from the backbone and then wash 
all the blood out of the fish. 

These and other similar observations showed the importance of 
the mode of cleaning as a factor in fish salting. A series of experi- 
ments was, therefore, carried out for the purpose of learning which 
method of preparing fish for salting was the best. 

(■():\IXIK1;C1AL METHODS OF CLEANING. 

Uncut fish. — Large quantities of herring and alewives are annually 
salted round, or without cutting. Some of these are washed, but 
other fish salters do not wash their round fish. . 

Pipping. — When herring are salted by the Scotch method, they are 
pij^ped or gibbed. This involves the cutting of the fish at the throat 
so that the gills and viscera are all removed, with the exception of 
the milt and roe. The head is not cut off. ^Vlien fish are cut in this 
way it is difficult to remove the blood contained in the abdominal 
cavity. 

Beheading. — " Pleadless roe " fish are prepared by partially cutting 
off the head of a roe fish usually river herring; then the head is 
pulled off in such a way tliat the viscera, with the exception of the 
roe, are i)ulled out. Little blood may be washed out from fish 
cleaned in this manner. In some cases this procedure is altered by 
cutting the fish down the belly in addition to beheading. 

Cutting. — The greater proportion of the river herring are salted 
after the heads and bellies have been cut off. In most cases this is 
done by the cutter in one operation. 

Cutting anxl scrafing. — In some vicinities small quantities of river 
herring are salted after being cleaned perfectly. The heads and 
bellies are cut off. and then the abdominal cavity is scraped until all 
the blood under the backbone and all the membranes are removed. 
Fish cleaned in this way are usually consumed locally. 

Splitting. — Larger fish, such as the mackerel, cod, haddock, cusk, 
and the like, are usually eviscerated and split. This is considered 
essential for proper salting. 

EFFECT OF CLEANING ON PROTEIN DECOMPOSITION. 



The worlv on cleaning was done on the river herring. Two hun- 
dred and fifty pounds of river herring were purchased from a local 
Albemarle Sound fisherman. These fish were iced as soon as thoy 
wei'e received from the boat, which was about two hours after their 
capture. The fish were divided into 8 lots : 2 lots of 1,000 grams 
each were salted I'ound : 2 other lots were pipped ; 2 lots were cleaned 
by cutting off the heads, cutting the fish the length of the belly, and 
removing the entrails, with the exception of the milt and roe; and 2 
lots were cleaned by cutting and scraping. The heads and viscera 
were removed, including the milt and roe. These fish were then Avell 
washed, and blood and membranes were scraped out of the abdomi- 
nal cavity. Great care was taken in this case to remove all visible 



THE SALTING OF FISH. 



45 



blood, including that undeineath the backbone. All the lots were 
then weighed out. Exactly 1,000 grams of cleaned fish were taken in 
each case. They were salted in dry Diamond Flake salt, which is- a 
fine, pure, granulated salt. Three and a third kilograms of salt were 
used on each lot during the fii'st packing. The following day 833 
grams of salt were added to each lot of fish. 

One lot cleaned in each way was placed in each of two constant 
temperature compartments, which have been previously described. 
One of these constant-temperature compartments was regulated for 
79° F. The other was set for 88° F. Both these temperatures, it 
will be noted, are very high for salting fish. The results of these 
experiments are given in Table 12. 

Table 12. — Devei.opment of A mi no-Acid Nitrogen in Fish Cleaned in Vaeioits 

Ways." 



Experiment No. 



BA-1 
BA-2 
BA-3 

BA-4 
BA-5 
BA-6 
BA-7 

BA-8 



Method ol cleaninj;. 



No cleaning; salted round 

Pipped 

Head out off; abdominal cavity split open; 

vis'^era remo\ed, with exception of milt 

and roe. 
Cleaned perfectly; milt and roe removed. . 

No cleaning; saltefj roimd 

Pipped 

Head cut off; abdominal cavity split open; 

viscera removed, with exception of milt 

and roe. 
Cleaned perfectly; milt and roe removed. . . 



Average 
tempera- 
ture of 
salting 
period. 



Weight I Amino-acid nitro- 
of fresh gen in fresh fish 
fish. I (4 hours). 




Per cent. 

0.029 

.027 

.022 



1,000 


.020 


1,000 


.029 


1,000 


.027 


1,000 


.022 



Grams. 
2.90 
2.70 
2.20 



2.00 
2.90 
2.70 
2.20 



1,000 





Total amino-acid nitrogen at end in — 


Amino-acid nitro- 
gen formed. 


Physical condition of 
fish. 


Erperfmnnt No. 


Fish. 


Brine. 


Rait. 


Fish, 

brine. 

and salt. 


Total. 


Per 
kilogram 
fresh fish. 


BA-l 


Grams. 
7.88 
6.66 
6.80 
3.83 
10.70 
7.75 
7.72 
4.60 


Grams. 
2.52 
2.09 
2.06 
1.70 
3.08 
2.40 
2.45 
1.95 


Grams. 
0.22 
.29 
.19 
.13 
.35 
.20 
.22 
.14 


Grams. 
10.62 
9.04 
9.05 
5.66 
14.13 
10.35 
10.39 
6.69 


Grams. 
7.72 
6.34 
6.85 
3.66 
11.23 
7.65 
8.19 
4.69 


Chrams. 
0.77 

.63 
.68 
.37 
1.12 
.76 
.82 
.47 


Badly spoiled: bloated. 
Spoiled. 
Do 


BA-2 


BA-3 


BA-4 




BA-6 


Badly spoiled; bloated. 
Badly spoiled. 


BA-6 


BA-7 


BA-8 

















a In this experiment the fish were dry salted for nine days, four hours after capture, with 4.16fi kiU; 
grams of Diamond Flake salt (90.78 per cent NaCli. 



DISCUSSION. 

The remaxkable thing about this experiment is that all the fish 
salted were entirely spoiled except those cleaned perfectly. Even the 
lot of perfectly cleaned fish which was salted at a temperature of 
88° F. throughout the salting period was found to be in perfect con- 
dition at the end. These fish were cooked and sampled by six per- 
sons. All pronounced them to be far superior to the commercial salt- 
fish product. One critic went so far as to say that they were on a 
par with the fresh river herring. 



46 



THE SALTING OF FISH. 



Fig 



Oray 



SKin 



Whr'fc 



Co/ Surface 

6. — Whitening of fish after 
1 day in brine. 



SRin 




The results of the chemical analyses for amino-acid nitrogen in the 
various samples verifies these observations. Both perfectly cleaned 

lots ran very low in amino acids. This 
shows definitely that there was very 
little protein decomposition. 

The i-esults given in Table 12 show 
that round fish spoil very easily when 
salted. This is a very poor way to salt 
fish unless the weather is very cold. On 
comparing BA-2 with BA-3, and BA-6 
with BA-T, the writer is forced to the 
conclusion that it makes very little dif- 
ference whether the fish are cut the 
length of the belly or not. It may be 
that those cut open. BA-3 and BA-7, 
were infected with bacteria during the 
process. At these high temperatures 
bacteria seem to thrive even in the pres- 
ence of the salt. This w^as evidenced 
by the bloating of all the round fish, 
due to the accumulation of gas in the 
belly. This also took place in some of 
the ^^ipped fish. 

The wa*iter wishes to point out that 
the only difference between lots BA-3 
and BA-4 and between lots BA-7 and 
BA-8 was that BA-3 and BA-7 con- 
tained milt, roe, and blood. These sub- 
stances were, then, alone responsible for 
the spoilage. No other factor could be 
the cause, as the procedure in handling 
was the same in every respect. The 
question then arises as to which caused 
the S])oilage — the blood, roe. or milt. 

Previously a similar experiment had 
been attempted, except that the work 
was carried out in a commercial plant 
and was merely qualitative. This 
experiment was not quite so suc- 
cessful, for at a lower temj^era- 
ture, 80° F.. some of the fish 
spoiled. However, the majority 
were in excellent condition. 
Upon examination, the spoiled 
fish revealed that the work of 
removal of blood before salting 
Whlt^ had been carelessly done, for 
blood was found under the back- 
bone, above the vent, in every 
spoiled fish. None of the good 
fish showed traces of blood. Un- 
fortunately, no attempt was made 
to salt milt and roe at high tem- 




Cut Surface 



Fig. 7. 



-Whitening of fish 
6 days in brine. 



after 



Gray 




SKin 



Cu/ Surface 



Fig. 8.- 



-Whitening of fiSh 
in brine. 



after 10 days 



THE SALTING OF FISH. 



47 



peratures. Such experiments would show whether these substances 
are partially responsible for the spoilage. Howe'ver, both the milt 
and roe must be removed if all of the blood be taken out of the fish. 
This is, therefore, a point of secondary impoi-tance. 



ACTION or THE SKIN. 



The skin of fish is known to be a membrane which is more or less 
impermeable to the passage of dissolved salts. In the work on pene- 
tration of different salts it was noted that the penetration of salt into 
the fish took place much more rapidly through the cut flesh than 
through fish covered with skin. In the experiments on the penetra- 
tion of salts containing calcium salts as impurity the passage of the 
salt into the fish could be followed verj^ easily, for as the salt passed 
into the fish the fish became very white. This gave an easy way of 
estimating the rate of penetration of the salt into the different parts 
of the fish. The fish were cut on different days. The depth of the 
whitening was measured and the cross sections were drawn to scale. 
The diagrams are given to show how mucli more rapid the penetration 
of the salt is through the cut surface than through the skin surface. 

Figure 6 shows the appearance of a cross section of a squeteague 
after it had been in salt for one day. The whitening had pene- 
trated 5 mm. on the cut surface, but the whitened condition was 
found only 1 mm. under the skin. Figure 7 shows a cross section 
of the fish after it had been salted for six days. At this time the 
line between the light and dark portions of the section was not so 
distinct. Figure 8 shows a section of the fish near the end of the 
salting period, which was 10 days. There is yet a portion of the fish 
which was not white. This shows that the fish as yet was not 
salted uniformly throughout. The fish became entirely white 
throughout on the thirteenth day. 

In order to gain a more accurate idea of tlw retardation of the 
penetration of the skin by the salt, some experiments were tried to 
determine the relative rate of penetration of salt into skinned and 
unskinned fish. In these experiments lioth skinned and unskinned 
squeteagues were salted in dry salt by the ordinary procedure, as 
described previously. Tlie salt used contained 1 per cent of calcium 
chloride. This is about the purity of tlie average salt used for the 
salting of fish. 

The penetration of the chlorides into the fish was determined by 
analyzing different sections of the fish from day to day. The pro- 
<^edure followed has been described in the first part of this paper. 
The results of the analyses of the sections from one-half centuneter 
to 1 cm. in depth are giAen in Table 13. 

Table 13. — Comparative Rate of Penetbation of Chlokibes " Into Skinned 

AND UnSKINNEH) FiSH,* EXPRESSED IN PeE CeNT OF CHLORINE IN DrY FiSH. 





Mode of cleaning. 


Per cent chlorine after— 




22 hours. 4 days. 


7 days. 


13 days. 


Skmned 


9. 7 1 19. S 
1.7 11.9 


20.2 
18.9 


20.3 


TTnsldimed - - - - - - - - - - 


20.3 









n Analysis of salt used, 99 per eent sodium ehloride, 1 por ornt caloium chloride. 
^ Inner section of fish, J to 1 cm. 



48 THE SAIiTING OF FISH. 



DISCUSSION. 



These data show that salt penetrates skinned fish at approximately 
double the speed it enters unskinned fish. Therefore, skinned fish 
may be salted in about one-half the time required for unskinned 
fish. Of course, it is not practical to skin most fish before salting; 
but these results show the great advantage gained in splitting a 
fish wherever this procedure may be followed. In hot climates the 
length of the salting period, the period of danger, may be cut in 
tw^o. 

St. Johns River shad are successfully salted in Florida by the 
present methods. Attempts at salting St. Johns River alewives have 
repeatedly failed. The reason for the successful salting of the shad 
may be because the shad are split and washed before salting. The 
alewives are salted without splitting. Due to this splitting, the salt- 
ing period of the shad may be shorter than the salting period for the 
alewives. 



PRACTICAL APPLICATIONS. 



This work on the methods of cleaning proves beyond doubt that 
the chief cause of spoilage of fish during salting in hot weather is 
the decomposition of the blood contained in the fish. This seems to 
show that the problem of salting fish in warm climates is in reality 
a very simple one. 

What must be done, then, in order to salt the alewives of the 
Florida rivers successfully during warm w^eather ? The only change 
from the North Carolina method necessary is that greater care must 
be taken to remove every bit of blood and viscera. This can be ac- 
complished if the roe and buckroe are removed in the cleaning opera- 
tion. These may be canned profitably. After cleaning, the under 
side of the backbone should be .scraped so that all the blood and mem- 
branes in the abdominal cavity are removed. A 20-penny nail is an 
instrument that can be conveniently used for scraping the backbone. 
The head of the nail may be ground thinner on an emery wheel. This 
operation sharpens the head so that it cuts out the membranes with- 
out much pressure. A single operator can easily scrape out a thou- 
sand fish in an hour. After scraping the fish they should be soaked 
in cold water for at least one-half hour. This dissolves practically 
every trace of the blood. It is good practice to wash the fish in a 
false-bottomed wheelbarrow with a powerful stream of water. After 
soaking the fish they should be packed in dry salt. 

The above method of cleaning fish pays, even though the salting is 
done in a climate where this procedure is not essential ; for extra 
washing and cleaning produces fish of nuich finer quality than those 
produced by the old methods. The up-to-date canner is using every 
possible precaution to avoid the ]>resence of blood in his canned fish, 
so as to produce an entirely white fish. The well- washed fish when 
salted does not undergo a discoloration due to the jjresence of blood. 
The strong taste of salted river hemng is eliminated in the washing. 

Perfectly cleaned fish, salted at high temperatures, should bring 
a hotter price than the old dirty-looking product ]:)roduced in the 
North. The public would soon learn of their im])rovcd quality. 

All large fish salted in warm weather should be s])lit. and care 
should be taken to remove the blood. This should be less difficult in 



THE SALTING OF FISH. 49 

the case of the split fish, for the blood would be almost entirely ex- 
posed to Anew. The splitting would also greatly decrease the length 
of the salting period, due to the more rapid penetration of the salt. 

SUMMARY. 

River herring, cleaned by A'arions methods, were malted at A'ery 
high temperatures. All save those from which all roe, milt, and 
blood had been removed spoiled. Perfectly cleaned river herring 
were salted at a temperature of 88° F. It was concluded, therefore, 
that tlie chief cause of spoilage of fish during salting is the decom- 
position of the blood remaining in the fish. The rate of penetration 
of salts into skinned fish was compared with the rate of penetration 
of salt into fish before skinning. It was found that salt penetrates 
skinned fish at about double the speed it enters unskinned fish. This 
proves the great value of splitting fish preparatory to salting. These 
results are of groat Aalue in a practical way, for they show that if 
proper care be taken in the cleaning of fish, it is probable that they 
may be salted in any hot Aveather anywhere in the United States. 
With only an hour's extra work per thousand of river herring, these 
fish may be prepared for salting in hot weather. The salt-fish prod- 
uct prepared by this extra care in cleaning is of much better quality 
than the commercial salt fish. 

IV. INFLUENCE OF FRESHNESS IN SALTING FISH. 
INTRODUCTION, 

Staleness in fish is undesirable. However, more or less staleness is 
always unavoidable. It seems reasonable to suppose that during 
colder weather staler fish may be salted than during hot weather. 
Few data in the literature concerning the limits of freshness are of 
value, for there are no standard methods of judging staleness. Most 
writers on the subject have used various physical criteria to estimate 
the relative freshness of stale fish. Some of the physical qualities 
that have been used as criteria are : 1. The presence, or absence, of a 
reddish discoloration on the ventral aspect of the backbone. 2. The 
odor. 3. The manner in which the flesh separates from the back- 
bone. 4. The appearance of the abdominal walls. 

The use of such criteria leaves too much to the judgment of the 
investigator. In other Avords, the personal equation plays too promi- 
nent a part. There are really but two ways of fairly stating the de- 
gree of freshness of any fish. The first and most accurate way is to 
give the number of hours since the fish was caught and the tempera- 
ture; at which it has stood for that time ; the other is to state its chemi- 
cal analysis. The per cents of amino-acid nitrogen and of ammoni- 
acal nitrogen are particularly indicative of the condition of the fish. 

In experiments previously described the number of hours the fish 
had been out of the Avater before they Avere salted has be'en given 
wherever possible. Since it was impossible to obtain live fish, stand- 
ard freshness was considered as a fish transported in a boat at atmos- 
pheric temperature for two hours. Then the fish Avere iced and 



50 



THE SALTING OF FISH. 



cleaned, and after being iced for two hours were salted. There was, 
of course, the error caused hj the difference in temperatures of differ- 
ent days. However, since at no time was the atmospheric tempera- 
ture above 80° F., little decomposition took place in the two hours. 

Since fish spoil so quickly during hot w^eather, an attempt was made 
to find out how fresh they must be in order successfully to salt them 
at various temperatures. This should show whether the cause of 
spoilage during salting in hot weather was through the use of stale 
fish. 

Insufficient work has been accomplished to obtain any very definite 
data concerning the nefcessary freshness of fish for salting. Unfortu- 
nately, the work was carried out at too high temperatures, and all of 
(he stale lots of fish spoiled. 

METHOD. 

Eighty pounds of glut herring {Pom£>lohws (vstivulis) were ob- 
tained after they had been out of the w^ater for four hours. During 
this time they had been kept at approximately 60° F. They were 
divided into five lots and kept at 64° F. One lot was immediately 
cleaned, washed, and dry salted according to the usual method. 
After 16 hours a second lot was cleaned, washed, and salted; and 
after 24 hours a third lot was cleaned, washed, and salted. The first 
three lots were cleaned by beheading and eviscerating the fish, with- 
out removing the milt and roe. After 33 hours the two remaining 
lots were cleaned and salted. One of these lots was cleaned in the 
same manner as that of the first three. The other was cleaned more 
perfectly. The milt and roe were taken out, and the blood was 
scraped out from under the backbone. These fish were given an 
extra washing. 

The five lots of fish were allowed to stand 15 days (from day of 
catch) before the analyses were made. For this reason the amounts 
of amino acids found were higher than in comparative lots which 
were analyzed at the end of nine days. The total amounts of amino- 
acid nitrogen formed were computed as before. The results are ariven 
in Table 14. 



Table 14. 



-Development of Amino- Acid Nitrogen in Fkestt ant) Stale Fish 
AT 64° F.« 



Exporimont Nn. 



Z-2. 
Z-3. 
Z-4. 

z-n. 



Time 
lictwoon 
ciiptnro 

and 
salting. 



Method of cleaning. 



Head and viscera removed, with the 
exception of the milt and roe; 
washed once in ice water. 

do 

do 

do 

Head, blood, and all viscera remo\ed: 
washed twice in ice water. 



Weight 

of fresh 

fish. 



Orams. 
6,000 



6,000 
6,000 
.'■>, oOO 
5, 500 



Amino-acld nitro- 
gen in fresh 

ri<ih. 



Per cent. 
0. 022 



.022 
.022 
.022 
.020 



Gramit. 
L32 



L32 

l:« 

1.21 
1.10 



o In this experiment t^e fish were dry salted for 15 days with 2,200 grams of chemically pure sodium 
chloride. 



THE SALTING OF FISH. 



51 



Tabie 14. — Development of Ami no-Acid NrrRixiEN in Fbksh and Stale Fish 

AT 64° F. — Continued. 





Total amino-acid at end in— 


Amino-acid formed. 




Experiment No. 


Fish. 


Brine. 


1 Fish, 
Salt, [brine, and 
1 salt. 

1 


Total. 


Per kilo- 
gram 
fresh fish. 


Physical condition 
of fish. 


Z_l 


Orams. 
5.06 

7.28 
7.86 
8.54 
4.54 


Orams. 
1.19 
1.51 
1.53 
1.60 
1.51 


Orams. 
0.51 
.43 
.44 
.40 
.30 


Grams. 
6.76 
9.22 
9.83 
10.54 
6.35 


Grams. 
5.44 
7.90 
8.51 
9.33 
5.25 


Grams. 
0.91 
1.32 
1.42 
1.70 
.95 


Good. 


Z-2 


Tainted. 


Z 3 


Spoiled. 


Z-4 


Badly spoiled. 


Z-5 


Tainted. 







DISCUSSION, 

Sixty-four degrees Fahrenheit is verj' close to the maximum tem- 
perature for salting fish containing blood, milt, and roe. For this 
reason all the stale fish spoiled. However, a comparison of the re- 
sults obtained in lots Z-4 and Z-5 shows quite plainly that the roe, 
milt, and blood are the first portions of a fish to spoil at lower 
temperatures. This suggests a method of dealing with all stale fish. 
Evidentl}^ much staler fish may be salted if they are perfectly 
cleaned than if they contain blood, milt, or roe. 

Two other experiments at higher temperatures were tried which 
verify these results. The other experiments were conducted at 75 
and 79° F., respectively, which temperatures were so high that all 
the fish spoiled. These experiments were almost exact duplicates of 
the experiments reported in Table 14; hence they will not be de- 
scribed in detail. The fish were cleaned and salted at 4, 10. 14, and 
28 hour intervals. Four lots of fish were kept at 75° and foyr at 
79° during this period. The 4, 10, and 14 hour lots were only par- 
tially cleaned, the roe. milt, and blood being left in and the fish 
washed but once. The 28-hour lots were cleaned perfectly, the roe 
and milt being removed and the blood scraped out. Lot Z-5 was 
treated in the same way. All of these lots were salted in brine. The 
results of the calculations of the total amounts of amino-acid nitro- 
gen formed are given in Table 15. 



Table 15. 



-De'stilopment of Amino-Acid Nitrogen in Fresh and Stale Fish 
AT 75 and 79° F.« 



Experiment No. 


Time 
between 
captm-e 

and 
salting. 


Method of cleaning. 


Average 
tempera- 
ture of 
salting 
period. 


Weight 

of fre.sh 

fish. 


Amino-acid nitro- 
gen in fresh 

fish 
(4hoiu-s). 


DA-S 


Hours. 
4 

10 
14 

28 

4 

10 
14 

28 


Head and viscera removed 
with exception of milt 
and roe. Washed once in 
ice water. 

do 


"F. 

75 

75 
75 
75 

79 

79 
79 
79 


Orams. 
.5,000 

5,000 
5,000 
5,000 

.5,000 

.5,000 
5,000 
5,000 


Per cent. 
0.022 

.022 
.022 
.020 

.022 

.022 
.022 
.020 


Orams. 
1.10 


DA-11 


1.10 


DA-12 


do 


1.10 


DA-14 


Head and all viscera re- 
moved. Blood washed 
out. 

Head and viscera removed 

with exception of milt and 

roe. Washed once in ice 

water. 

do 


1.00 


DA-1 


1.10 


DA-4 


1.10 


DA-5 


do 


1.10 


DA-7 : 


Head and viscera removed. 
Blood washed out. 


1.00 







« In this experiment the fish were salted for nine days in 5 liters of brine prepared from Diamond Flake 
salt f NaCl 99.78 per cent) and 1 kilogram of this salt. 



62 



THE SALTING OF FISH. 



Table 15. — Development of Amino-Acid Nitrogen in Fresh and^tale Fish 
AT 75 AND 79° F. — Continued. 



Experiment No. 


Total aniino-acid nitrogen at end 
in- 


Amino-acid nitrogen 
formed. 


Physical condition 


Fish. 


Brine. 


Fish, brine, 
and salt. 


Total. 


Per kilo- 
gram 
fresh fish. 


offish. 


DA-S 


Grams. 
2.46 
3.50 
3.36 
2.15 
3.00 
3.43 
3.64 
3.34 


Grams. 
2.09 
2.11 
2.45 
2.51 
2.00 
2.56 
2.71 
2.94 


Grams. 
4.55 
5.61 
5.81 
4.66 
5.00 
5.99 
6.35 
6.28 


Grams. 
3.45 
4.51 
4.71 
3.66 
3.90 
4.89 
5.25 
5.28 


Grams. 

0.69 

.90 

.94 

.73 

.78 

.98 

1.05 

1.06 


Tainted. 


DA-U 


Spoiled. 
Do. 


DA-12 


DA-14 


Tainted. 


DA-1 


Spoiled. 
Do. 


DA-4 


DA-5 

DA-7 


Badly spoiled. 
Spoiled. 







Comparisons of the analyses of lot DA-12 with the analyses of 
lot DA-14 and of DA-5 with DA-7 show that thorough cleaning 
permits the salting of staler fish, for there was no more decomposi- 
tion in the case of the thoroughly cleaned 28-hour fish than in the 
case of the 14-hour fish containing milt, blood, and roe. A compari- 
son of DA-8 with DA-11 plainly indicates that at high tempera- 
tures great care must be taken to obtain absolutely fresh fish for 
salting. Evidently there is a temperature somewhere between 50 
and 60° F., above which fish can not be kept for any length of time 
without spoiling. 



GENERAL CONCLUSIONS. 

I. InfAience of impwrities in scdt in salting fish. — Calcium and 
magnesium salts and sulphates, as impurities in salt, retard the 
penetration of salt into fish. Salts containing these impurities, there- 
fore, cause fish to spoil during salting at a lower temperature than 
salts not containing such impurities. Of these three impurities, 
calcium is the only one present in commercial salts in large enough 
quantities to have an appreciable effect on the quality of the salt. 

II. A compariso-n, of the efficiency of hrine and dry salt for salting 
fish. — Fish packed in dry salt, without any addition of brine, may 
be kept at a higher temperature than fish salted in brine, for less 
decomposition takes place if no brine be added. The dry-salt method 
is the more economical method of the two. 

III. Influence of method of clemming fish for saltvng. — The re- 
moval of all blood and viscera, including roe and milt, is absolutely 
essential for the salting of fish at high temperatures. Blood spoils 
at a temperature at least 25° F. lower than the spoilage temperature 
of the flesh of fish. 

IV. Influence of freshness in salti/ng fish. — During warm weather 
freshness of fish is essential to successful salting. However, much 
staler fish may be salted if all blood, roe, and milt are removed in 
cleaning. 

RELATIVE IMPORTANCE OF FACTORS. 

The predominant factor in controlling the qualities of the salt- 
fish product and the maximum temperature of salting is the thorough 
cleaning of the fish, so as to effect the removal ot all viscera and 
blood. If fish are perfectly cleaned, it appears possible to obtain a 
white, sweet-tasting salt fish at any American summer temperature. 
If the fish are not perfectly cleaned, it is impossible to salt them at 
any temperature averaging above 70° F. by any known method of 
salting, regardless of the kind of salt used or the mode of applica-' 
tion of the salt. 

The factor of second importance is freshness. When the tem- 
perature of the fish is above 70° F., the fish must be salted the same 
day that they are caught, if they are to be successfully cured. At 
lower temperatures this factor is of less importance, until at 32° F. 
this factor is practically eliminated. That is to say, at this tempera- 
ture fish may be kept for long periods and yet be salted successfully. 

Next in line of importance comes the method of application of 
salt. Fish iced for two days (see p. 36) may be salted at about 
4° higher temperature by the application of dry salt rather than 
brine. Fine salt must be used for small fish. 

Of next importance is the composition of the salt. This factor 
may be easily controlled by the purchase of salt of known purity. 
This affects the physical qualities of the salt fish. Commercial salts 
high in calcium lower the maximum temperature at which fisli may 
be salted by any known method. 

53 



54 THE SALTING OF FISH. 

PRACTICAL APPLICATIONS OF RESULTS. • 

The probability that fresh fish may be salted without danger of 
spoilage in any climate in the United States is of considerable im- 
portance. The only reqnireinents for salting fish at high summer 
temperatures are : 

1. All viscera and blood must be removed in cleaning. 

2. All large fish must be split. 

3. The fish must be salted in a reasonably fresh condition. 

4. No brine should be added in salting. 

5. Salts low in calcium must be chosen. 

These requirements do not involve great changes in the methods 
of salting now employed. In reality they merely require more per- 
fect cleaning and greater care in the selection of salt. The fish of our 
southern waters that are as yet not utilized may be salted without any 
difficult changes in the present methods, and thus a great saving may 
be effected. 



I 



BIBLIOGRAPHY. 

Benedict, S. R., and Mublin, J. R. 

1913. Note on the determination of aniino-acid nitrogen in urine. The 
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Baltimore. 

Bitting, A. W. 

1911. Preparation of the cod and other salt, fish for the market : Includ- 
ing a bacteriological study of the causes of reddening. U. S. De- 
partment of Agriculture, Bureau of Chemistry Bulletin No. 133, 
63 pp., 6 pis., 4 figs. Washington. 

BBADI.EY, H. C, and Tatlob, Joseph. 

1917. Studies of autolysis. V. The influence of bile on autolysis. The 

Journal of Biological Chemistry, Vol. XXIX, No. 1, pp. 281-288. 
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Ci^BK, E. D., and Almt, L. H. 

1918. A chemical study of food fishes. The analysis of 20 common food 

fishes, with especial reference to a seasonal variation in composi- 
tion. The Journal of Biological Chendstry, Vol. XXXIII, No. 3, 
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HoAGLAND, Ralph, McBeide, Charles N., and Powick, Wilmesi C. 

1917. Changes in fresh beef during cold storage above freezing. U. S. 
Department of Agriculture Bulletin No. 433, contribution from the 
Bureau of Animal Industry, lOU pp., 2 tigs. Washington. 
Ottolenghi, D. 

1913. Studien Uber die Reifung und Zersetzung des Fleisches. Zeitschrift 
fur Untersuchung der Nahrungs- und Genussmittel, sov?ie der 
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Phalen, W. C. 

1917. Technology of salt making in the United States. Department of the 
Interior, Bureau of Mines Bulletin 146, Mineral Technology 20, 
149 pp., 24 pis., 10 figs. Washington. 

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